Antonio Battaglia

The effect of testosterone on regional blood flow in prepubertal anaesthetized pigs.

This work was undertaken to study the effects of testosterone on the coronary, mesenteric, renal and iliac circulations and to determine the mechanisms of action involved. In prepubertal pigs of both sexes anaesthetized with sodium pentobarbitone, changes in left circumflex or anterior descending coronary, superior mesenteric, left renal and left external iliac blood flow caused by intra‐arterial infusion of testosterone were assessed using electromagnetic flowmeters. Changes in heart rate and arterial blood pressure were prevented by atrial pacing and by connecting the arterial system to a pressurized reservoir containing Ringer solution. In 12 pigs, intra‐arterial infusion of testosterone for 5 min to achieve a stable intra‐arterial concentration of 1 μg l−1 increased coronary, mesenteric, renal and iliac blood flow without affecting the maximum rate of change of left ventricular systolic pressure (left ventricular dP/dtmax) and filling pressures of the heart. In a further five pigs, a concentration‐response curve was obtained by graded increases in the intra‐arterial concentration of the hormone between 0.125 and 8 μg l−1. The mechanisms of these responses were studied in the 12 pigs by repeating the experiment after haemodynamic variables had returned to the control values before infusions. In six pigs, blockade of muscarinic cholinoceptors and adrenoceptors with atropine, propranolol and phentolamine did not affect the responses caused by intra‐arterial infusion of testosterone performed to achieve a stable intra‐arterial concentration of 1 μg l−1. In the same pigs and in the remaining six pigs, the increases in coronary, mesenteric, renal and iliac blood flow caused by intra‐arterial infusion of testosterone performed to achieve a stable intra‐arterial concentration of 1 μg l−1 were prevented by intra‐arterial injection of Nω‐nitro‐L‐arginine methyl ester. The present study shows that intra‐arterial infusion of testosterone dilated coronary, mesenteric, renal and iliac circulations. The mechanism of this response involved the release of nitric oxide.

The effect of 17β‐oestradiol on regional blood flow in anaesthetized pigs

1 The present study was designed to investigate the effects of 17β‐oestradiol on the mesenteric, renal, iliac and coronary circulations and to determine the mechanisms involved. 2 In pigs anaesthetized with sodium pentobarbitone, changes in blood flow in the superior mesenteric, left renal, left external iliac and left circumflex coronary arteries caused by intravenous infusion of 17β‐oestradiol at constant heart rate and arterial pressure were assessed using electromagnetic flowmeters. 3 In eight pigs, infusion of 2 μg h−1 of the hormone caused an increase in renal, iliac and coronary blood flow without affecting mesenteric blood flow, left ventricular dP/dtmax (rate of change of left ventricular systolic pressure) and filling pressures of the heart. In four pigs, these vasodilator effects were enhanced by graded increases in the dose of the hormone between 1, 2 and 3 μg h−1; the highest dose also caused an increase in mesenteric blood flow. 4 In five pigs, blockade of muscarinic cholinoceptors and adrenoceptors with the intravenous administration of atropine, propranolol and phentolamine did not affect the vasodilator responses caused by infusion of 2 μg h−1 of 17β‐oestradiol. 5 The increases in renal, iliac and coronary blood flow caused by infusion of 2 μg h−1 of 17β‐oestradiol were prevented, respectively, by the injection of Nω‐nitro‐L‐arginine methyl ester (L‐NAME) into the renal artery (five pigs), the iliac artery (five pigs) or the coronary artery (five pigs). In five pigs, all responses were prevented by injection of L‐NAME into all three arteries. In two pigs, injection of L‐NAME into the mesenteric, renal, iliac and coronary arteries abolished the vasodilator responses to the infusion of 3 μg h−1 of 17β‐oestradiol. 6 The present study shows that intravenous infusion of 2 μg h−1 of 17β‐oestradiol primarily dilated renal, iliac and coronary circulations and that a higher dose of the hormone also caused vasodilatation in the mesenteric vascular bed. The mechanism of these responses was shown to be nitric oxide dependent.

The effects of hypertonic saline solution on coronary blood flow in anaesthetized pigs.

1. The effects of intracoronary bolus infusion of hypertonic saline solution on left circumflex coronary blood flow were examined in sixteen anaesthetized and artificially ventilated pigs whilst preventing changes in heart rate and arterial blood pressure. 2. In fourteen pigs, bolus infusion of 7.5% hypertonic saline solution (2 ml within 30 s) caused a steady‐state increase in coronary blood flow without significantly affecting right atrial or left ventricular pressure and its rate of rise (dP/dtmax). Infusing normal saline solution (0.9%) at the same rate and volume in seven pigs did not have this effect. 3. In five pigs, the magnitude and the duration of the response of increase in coronary blood flow were increased in a graded manner by graded increases in the concentration of the hypertonic saline solution between 2.5, 5 and 7.5%. 4. In nine pigs, the response of increase in coronary blood flow to the bolus infusion of hypertonic saline solution was not affected by the blocking agents atropine, propranolol and phentolamine, but it was completely abolished in the same nine pigs by the subsequent intracoronary administration of N omega‐nitro‐L‐arginine methyl ester (L‐NAME) which blocks the synthesis of endothelium‐derived relaxing factor (EDRF) and in seven pigs by solely giving L‐NAME. 5. These results showed that the intracoronary bolus infusion of hypertonic saline solution in anaesthetized pigs caused a coronary vasodilatation which involved mechanisms dependent on the release of EDRF.

Reflex Coronary Vasoconstriction Caused by Gallbladder Distension in Anesthetized Pigs

BACKGROUND Gallbladder distension in anesthetized pigs reflexly increases heart rate and arterial pressure by means of afferent vagal pathways and efferent sympathetic mechanisms. The effect of such distension on the coronary circulation is unknown. The present study was undertaken to determine whether gallbladder distension primarily causes reflex changes in left circumflex blood flow. METHODS AND RESULTS In 21 pigs anesthetized with sodium pentobarbitone (16) or alpha-chloralose (5), left circumflex blood flow was measured with an electromagnetic flowmeter. A balloon positioned within the gallbladder was distended with volumes of Ringers solution equal to the volumes of bile previously withdrawn (mean vol: 62 mL; mean gallbladder pressure: 12 mm Hg). Heart rate and arterial pressure were kept constant by atrial pacing and by a pressurized reservoir connected to the left femoral artery. Gallbladder distension always caused a decrease in circumflex blood flow. In 6 of the 16 sodium pentobarbitone-anesthetized pigs, this decrease was graded by step increments of distension. In 5 of these 16 pigs, the decrease in circumflex blood flow was not affected by atropine. In 10 of these 16 pigs, including those given atropine, the response was not affected by propranolol but was abolished by subsequently giving phentolamine. Cervical vagotomy abolished the coronary vasoconstriction in the remaining 6 pigs. In the 5 alpha-chloralose-anesthetized pigs, the response was not significantly affected by cutting the splanchnic nerves but was abolished by subsequent cervical vagotomy. CONCLUSIONS The present study showed that innocuous distension of the gallbladder in anesthetized pigs caused a reflex coronary vasoconstriction that involved efferent sympathetic mechanisms related to alpha-adrenoceptors and afferent vagal pathways.

Role of nitric oxide in the control of the heart rate within the nucleus ambiguus of rats.

The aim of this study was to determine whether NO plays a role in the control of heart rate (HR) within the nucleus ambiguus (NA). Experiments were performed in 29 male Wistar rats anaesthetized with urethane. Microinjections of the NO-donor sodium nitroprusside (SNP; 5 mmol) as well as of L-arginine (L-arg; 50 mmol) into functionally identified cardioinhibitory sites within the NA significantly decreased HR (−57.7 ± 8.4 and −53.8 ± 3.2 bpm, respectively), whereas the NO-synthase inhibitor Nω-nitro-L-arginine methyl ester (L-NAME) significantly increased HR (+40 ± 2.7 bpm). Bilateral vagotomy and i.v. injection of atropine (0.5 mg/kg) always abolished the HR decrease induced by SNP and L-arg, whereas propranolol did not affect the HR responses. These results demonstrated that NO mechanisms within the NA play a role in the parasympathetic control of the HR.

The Effect of Dehydroepiandrosterone on Coronary Blood Flow in Prepubertal Anaesthetized Pigs

Extensive research suspecting an association between plasma levels of dehydroepiandrosterone and the risk of coronary heart disease has not been conclusive. The present study was designed to investigate the effect of dehydroepiandrosterone on the coronary circulation and to determine the mechanisms involved. In prepubertal pigs of both sexes anaesthetized with sodium pentobarbitone, changes in left circumflex or anterior descending coronary flow caused by intravenous infusion of dehydroepiandrosterone were assessed using an electromagnetic flowmeter. Changes in heart rate and arterial pressure were prevented by atrial pacing and by connecting the arterial system to a pressurized reservoir containing Ringer solution. In 20 pigs, infusion of 1 mg h−1 of dehydroepiandrosterone caused a decrease in coronary flow without affecting left ventricular dP/dtmax (rate of change of left ventricular systolic pressure) and filling pressures of the heart. In a further eight pigs, a dose–response curve was obtained by graded increases in the infused dose of hormone between 0.03 and 4 mg h−1. The mechanisms of the above response were studied in the 20 pigs by repeating the experiment after haemodynamic variables had returned to the control values observed before infusion. Blockade of muscarinic cholinoceptors with intravenous atropine (five pigs) and of α‐adrenoceptors with intravenous phentolamine (five pigs) did not affect the dehydroepiandrosterone‐induced coronary vasoconstriction. This response was abolished by blockade of β‐adrenoceptors with intravenous propranolol (five pigs) and of coronary nitric oxide synthase with intracoronary injection of Nω‐nitro‐l‐arginine methyl ester (five pigs) even after reversing the increase in arterial pressure and coronary vascular resistance caused by the two blocking agents with intravenous infusion of papaverine. The present study showed that intravenous infusion of dehydroepiandrosterone primarily caused coronary vasoconstriction. The mechanisms of this response were shown to involve the inhibition of a vasodilatory β‐adrenergic receptor‐mediated effect related to the release of nitric oxide.

Coronary effects of cyclovirobuxine D in anesthetized pigs and in isolated porcine coronary arteries

The present study was undertaken in anesthetized pigs and in isolated porcine coronary arteries to determine the primary coronary effects of cyclovirobuxine D. In six pigs, the intravenous administration of 1.5 mg/kg of cyclovirobuxine D whilst preventing changes in heart rate and aortic blood pressure caused increases in left ventricular dP/dtmax and coronary blood flow which respectively averaged 10% and 23.9%. These responses were progressively augmented by graded increases in the dose of the drug (four pigs) and were not affected by blockade of cholinergic and adrenergic receptors (five pigs). Intravenous blockade of nitric oxide synthase (L-NAME, five pigs) abolished both responses, while intracoronary injection of L-NAME (five pigs) abolished only the coronary vasodilatation. In ten isolated coronary segments, cyclovirobuxine D significantly reduced the degree of potassium chloride-induced contraction. This reduction was not affected by inhibition of cyclooxygenase with indomethacin (five segments) or potassium channels blockade with glibenclamide (five segments), but it was abolished by L-NAME (five segments) or removal of endothelium (five segments). The present study showed that cyclovirobuxine D caused a primary effect of coronary vasodilatation, which involved mechanisms related to the endothelial release of nitric oxide.

The effect of dehydroepiandrosterone on regional blood flow in prepubertal anaesthetized pigs: Dehydroepiandrosterone and regional flow

Dehydroepiandrosterone has been implicated in vascular disease and its associated insulin resistance and hypertension, though little is known about its vascular effects. We have recently shown in prepubertal anaesthetized pigs that intravenous infusion of dehydroepiandrosterone caused coronary vasoconstriction through the inhibition of a vasodilatory β‐adrenergic receptor‐mediated effect related to the release of nitric oxide. The present study was designed to investigate the effect of dehydroepiandrosterone on mesenteric, renal and iliac vascular beds. In prepubertal pigs of both sexes anaesthetized with sodium pentobarbitone, changes in superior mesenteric, left renal and left external iliac blood flow caused by intravenous infusion of dehydroepiandrosterone were assessed using electromagnetic flowmeters. Changes in heart rate and arterial blood pressure were prevented by atrial pacing and by connecting the arterial system to a pressurized reservoir containing Ringer solution. In 22 pigs, infusion of 1 mg h−1 of dehydroepiandrosterone decreased mesenteric, renal and iliac blood flow. In a further 10 pigs, dose–response curves were obtained by graded increases in the infused dose of hormone between 0.03 and 4 mg h−1. The mechanisms of the above response were studied in the 22 pigs by repeating the experiment after haemodynamic variables had returned to the control values observed before infusion. Blockade of α‐adrenoceptors with intravenous phentolamine (five pigs) did not affect the dehydroepiandrosterone‐induced mesenteric, renal and iliac vasoconstriction. This response was abolished by blockade of β2‐adrenoceptors with intravenous butoxamine (five pigs) and by blockade of mesenteric, renal and iliac nitric oxide synthase with intra‐arterial administration of Nω‐nitro‐l‐arginine methyl ester (seven pigs), even after reversing the increase in local vascular resistance caused by the two blocking agents with intravenous infusion of papaverine. In five pigs, the increase in measured blood flow caused by intravenous infusion of isoproterenol (isoprenaline) was significantly reduced by infusion of dehydroepiandrosterone. The present study showed that intravenous infusion of dehydroepiandrosterone primarily caused mesenteric, renal and iliac vasoconstriction. The mechanisms of this response were shown to be due to the inhibition of a vasodilatory β2‐adrenergic receptor‐mediated effect, which possibly involved the release of nitric oxide.

Changes in regional blood flow in response to distension of the uterus in anaesthetised pigs.

The present study was undertaken in anaesthetised pigs to determine the primary reflex effects of distension of the uterus on the peripheral circulation. Experiments were performed in seven pigs anaesthetised with alpha-chloralose and artificially ventilated. Blood flow in the superior mesenteric, left renal and left external iliac arteries was assessed using electromagnetic flowmeters. Distension of the uterus was performed whilst preventing changes in heart rate and aortic blood pressure by injecting 20 ml of warm Ringer solution in a balloon positioned within the viscus (mean transmural pressure of about 18 mmHg). In each pig, distension of the uterus caused decreases in all measured blood flows. In four pigs, these decreases were graded by step increments of distension. In the seven pigs, the responses of decrease in mesenteric, renal and iliac blood flows were not affected by blockade of beta-adrenergic receptors with propranolol, but were abolished by the subsequent blockade of alpha-adrenergic receptors with phentolamine. The present study showed that distension of the uterus in anaesthetised pigs primarily caused reflex vasoconstriction in the mesenteric, renal and iliac vascular beds. This reflex response was mediated by sympathetic mechanisms which involved alpha vascular adrenergic receptors.

Mechanisms of the renal vasodilation caused by insulin in anesthetized pigs.

The present study was planned to determine the mechanisms involved in the renal vasodilation caused by insulin. Changes in flow caused by the intravenous infusion of 0.004 IU/kg/min of insulin at constant heart rate, aortic blood pressure, left ventricular contractility and blood levels of glucose and potassium in the left renal artery were assessed using an electromagnetic flowmeter. In ten pigs, infusion of insulin caused an increase in renal blood flow which averaged 12.8% of the control values. After hemodynamic variables had returned to control values, insulin infusion was repeated in five pigs following blockade of alpha-adrenergic receptors with injection of phentolamine into the renal artery and in the other five pigs following blockade of nitric oxide formation with injection in the same artery of Nomega-nitro-L-arginine methyl ester (L-NAME). After blockade of alpha-adrenergic receptors, insulin infusion caused an increase in renal blood flow which averaged 18.1% of the control values, being significantly enhanced with respect to the increase previously obtained in the same pigs. On the contrary, after blockade of nitric oxide formation insulin infusion caused a decrease in renal blood flow which averaged 6.5% of the control values. These responses were respectively abolished by the subsequent injection into the renal artery of L-NAME and phentolamine. The present study showed that the renal vasodilation caused by insulin in the anesthetized pig was the result of two opposite effects which involved a predominant vasodilation mediated by the release of nitric oxide from the endothelium and a sympathetic vasoconstrictor mechanism mediated by alpha-adrenergic receptors.