L. Bjellin

β-Adrenergic control of motility in the rat colon. I. Evidence for functional separation of the β1- and β2-adrenoceptor-mediated inhibition of colon activity

Abstract The β-adrenoceptor-mediated inhibitory response in isolated rat colon strips of β-adrenoceptor agonists (isoproterenol, terbutaline, prenalterol) in the absence and presence of the selective β-adrenoceptor antagonists metoprolol ( β 1 ) and IPS 339 ( β 2 ) demonstrates that both β 1 - and β 2 -adrenoceptors are involved in the inhibition of colonic motility. Neuronal blockade induced by tetrodotoxin suppressed the relatively high (68%) maximal response of prenalterol (partial β-adrenoceptor agonist) to 23%. The concentration-response curves for terbutaline ( β 2 -selective agonist) and isoproterenol (nonselective agonist) were not influenced by tetrodotoxin. The results thus indicate that the β-adrenergic inhibition of spontaneous activity in the rat colon strip may be mediated at two functional levels within the colon wall: either by β 2 -adrenoceptors in the smooth muscle layer or by β 1 -adrenoceptors in the intramural ganglionic plexuses, which by neuronal elements are coupled to the effector smooth muscle.

Effect of terbutaline sulphate on ovarian, uterine and maternal placental blood flow in the anaesthetized guinea pig

The effect of terbutaline sulphage, a beta-adrenergic agonist, on uteroplacental blood flow was studied in the guinea pig during late pregnancy. Organ blood flows and cardiac output were assessed by the radioactive microsphere technique. Infusion of terbutaline at a rate of 2nmol min-1 kg-1 body weight caused a significant increase in cardiac output and in the perfusion of the uterus and ovaries, but there was no significant alteration in maternal placental blood flow. When the infusion rate was increased tenfold, there was also a significant rise in the blood supply to the bronchi, urinary bladder, kidneys, and adrenal glands. Maternal placental blood flow was not adversely affected even by this large dose of the drug, although there was a significant reduction in the placental share of the cardiac output.

Effect of 1-deamini-6-carba-(8-arginine)-vasopressin on organ blood flow in the female guinea pig

An analogue of (8-arginine)-vasopressin, characterized by removal of the Nalpha-amino group and replacement of the disulphide bridge with a thioether bridge (dCAVP), was found to increase blood flow to the brain, kidneys and adrenal glands of female guinea pigs whilst decreasing perfusion of the skin and skeletal muscle. An increase was noted in the proportion of 15 micrometer microspheres trapped in the spleen, probably contingent upon reduced arteriole-venous shunting. These responses were obtained both at estrus and during the luteal phase of the estrous cycle. In contrast, uterine and vaginal blood flows showed a significant reduction only during the luteal phase.

External113Inm and99Tcm radiation detection of lung edema induced by oleic acid in the guinea pig

SummaryThe establishment of a small animal model for studies of lung injury is in great demand. Therefore, a double radioisotope labeling method was applied to study the dynamics of lung injury with protein-rich edema in the anesthetized guinea pig. One external scintillation detector was placed over the lung and another over the heart, where they continuously sampled the energy spectrum of113Inm labeled transferrin, a macromolecular marker, and99Tcm labeled red blood cells (RBC), a blood pool marker. Lung injury was induced by i.v. oleic acid in doses of 0.03 and 0.06 ml/kg b.wt. infused for 10 min. We calculated the rate of increase of accumulated113Inm-transferrin in the lung corrected for blood pool changes. Macromolecular leakage showed a graded response in regression line-slope (RLS) to oleic acid. Both oleic acid groups showed significantly different RLSs as compared to the saline control (mean ± SD × 10−3 min−1; 0.03 ml: 3.86 ± 1.01 (n = 7); 0.06 ml: 10.75 ± 4.06 (n = 6), and control 1.12 ± 1.19 (n = 6)). Assays of changes of acid-base balance, cell dynamics, and lung wet-dry weight were in accordance with the occurrence of lung edema. The RLS was well correlated with the lung wet-dry weight (r = 0.98). We conclude that measurements of pulmonary edema in guinea pigs can be performed quantitatively with the aid of external detection of radiolabeled transferrin and RBC:s. Thus, the method could be useful in further studies on mechanisms and/or treatment of protein-rich lung edema.

THE EFFECT OF LONG TERM TREATMENT WITH A β‐ADRENOCEPTOR BLOCKER, l‐PROPRANOLOL, ON THE DISTRIBUTION OF CARDIAC OUTPUT OF THE LATE GESTATIONAL GUINEA‐PIG

The effects of daily administration of propranolol on the distribution of cardiac output were studied in the late pregnant guinea‐pig.