Angelo Cavatorta

Intracellular free [Ca2+] in circulating lymphocytes of spontaneously hypertensive rats

In the light of previous reports suggesting a common abnormality of Ca handling in most tissues of hypertensive humans and rats, we applied a novel technique using the fluorescent probe Quin 2 for measurement of cytosolic free Ca2+ in lymphocytes of spontaneously hypertensive rats (SHR). (Ca2+)i is increased in SHR (122.1 +/- 7.4 nM) versus normotensive Wistar-Kyoto (WKY) control rats (81.1 +/- 6.3 nM) Membrane exchange, as challenged by varying the extracellular Ca concentration over a 10(5)-fold range proved to be relatively unimportant in regulating (Ca2+)i and did not significantly affect the difference between SHR and WKY. Catecholamines and ouabain had no appreciable effect on (Ca2+)i. The mechanisms of increased (Ca2+)i in SHR lymphocytes remain to be fully elucidated.

The mechanism of Ca2+i increase in blood cells of spontaneously hypertensive rats.

Cytoplasmic free calcium (Ca2+i) is increased in platelets and lymphocytes of spontaneously hypertensive rats (SHR) and, to a lesser extent, in essential hypertensive patients. In this study, a method was devised to evaluate cellular Ca fluxes and the cellular Ca buffering power by means of the intracellular Ca indicator Quin-2. Ca influx was measured under conditions of Ca-pump inhibition, either by vanadate or ATP depletion. Lymphocytes of 5-month-old SHR were compared with those of normotensive Wistar-Kyoto rats (WKY). In both strains, the Ca entry rate and the cellular buffering capacity were higher in vanadate-treated than in ATP-depleted cells. SH rats exhibited a higher Ca influx and a greater intracellular Ca buffering power when vanadate was used to stop the Ca pump; these differences, however, were abolished in ATP-depleted lymphocytes. It is suggested that Ca entry in lymphocytes is ATP-dependent. Accelerated Ca entry in SHR can account for the previously reported higher levels of intracellular free Ca.

Isradipine in chronic renal failure: Antihypertensive effect and renal protection

Abstract Arterial hypertension is regarded as a major factor in the progression of chronic renal failure. Hyperfiltration in the surviving nephrons and increased protein leakage across the glomerular capillaries are thought to play a pathogenetic role. The effects of long-term treatment with the sustained-release formulation (SRO) of isradipine on blood pressure, renal function, and protein excretion were evaluated in patients with mild-to-moderate arterial hypertension and chronic renal failure (creatinine clearance 30 to 60 mL/min/1.73 m 2 ). Sixty-two patients (mean ± SD age, 56 ± 11 years) were included in the study. After a 14-day placebo period, a single 2.5-mg dose of isradipine SRO was administered each morning for 2 weeks. The dose was then increased to 5 mg/d if supine diastolic blood pressure (DBP) was ≥95 mm Hg; if adequate blood pressure control was not achieved, atenolol 25 to 100 mg or captopril 25 to 50 mg was added beginning at week 9. Thirty-six patients continued monotherapy throughout the study. After 8 weeks, mean casual blood pressure reduction was 10/7 mm Hg ( P P P P P = NS). Proteinuria decreased, although statistical significance was not achieved; median value for protein excretion in the urine collected during the night at week 24 was 361 mg compared with 755 mg at baseline ( P = 0.07). A similar decrease was apparent for protein fractions with different molecular weights (albumin, alpha 1 -microglobulin, retinol-binding protein, and beta 2 -microglobulin). Six patients (10%) reported minor side effects (flushing, ankle edema), none of which caused discontinuation of therapy. Long-term therapy with isradipine SRO is effective and well tolerated in patients with chronic renal failure; in addition, renal function appears to be preserved. Blood pressure reduction appears to favorably affect proteinuria and albuminuria; decreases in both are also desirable in antihypertensive therapy.

Adrenoceptor Alterations in Different Tissues in Human and Animal Genetic Hypertension

It is scarcely necessary to stress the importance of adrenoceptor regulation in arterial hypertension. In this disease an altered response to adrenergic agonists has been described in different organs, and particularly in the blood vessels [1–6]. Moreover, antiadrenergic drugs, and particularly alpha and beta blockers, are effective antihypertensive agents.

The Relationship between Myoplasmic Calcium and Force Developed during Stimulation of Arterial Smooth Muscle: A Study with Fura 2

Calcium is believed to play a primary role in vascular contraction, but quantitative simultaneous measurements of free intracellular calcium (hereafter: Ca;+) and force have not been reported. Novel intracellular calcium indicators, like Fura 2, provide this opportunity.’ Rat (Wistar-Kyoto, 8-9 weeks old) aortic medial rings were prepared by removal of adventitia and intima. The smooth muscle rings (1.5 mm wide, about 50 Fm thick) were light-microscopically intact and developed about 100% of force developed by intact whole aortic rings. They were mounted between two parallel pins in a 20 ml chamber with quartz windows. The lower pin was immovable, while the upper one was connected to a very rigid (0.02 mm displacement per gram force) tension transducer. The rigidity of the transducer ensured that little geometrical changes took place during stimulation and contraction of smooth muscle samples. The chamber was held in the sample compartment of a Perkin-Elmer MPF44A spectrofluorimeter in the position normally occupied by ordinary cuvettes. The smooth muscle tissue was loaded with 10-20 r M Fura2-AM (resulting in 100-200 p M intracellular free dye, with signals 8-1 0 times higher than basal autofluorescence). Preparations were excited alternately at 340-380 nm by motorizing the shaft of the excitation monochromator. The emitted fluorescence was recorded at 510 nm. The 340/380 ratios were used to calculate Cat+ as previously described,’ using a calibration curve obtained by exposing the samples to 10 FM ionomycin in the presence of 1 nM-1 mM extracellular calcium (Ca:+). The results of this study suggest the following conclusions: (1) the level of myoplasmic calcium is crucial for contraction, but (2) factors that increase the force:CaT+ ratio are equally important. Conclusion (1) is suggested by the fact that under any condition (including norepinephrine (NE) and high K stimulation) the level of force was proportional to CaT+ (FIGS. 1 and 2 ) and that raising Ca:+ “forcefully” with a ionophore (ionomycin) evoked Ca:’-dependent contractions. On the other hand conclusion (2) is supported by the findings that in the initial, phasic portion of high K and NE contraction, one observes a rapid increase in force without any major increase in Cat+; the phasic onset of stimulation is characterized by an increase of the force:CaT+ ratio, which is maintained as long as stimulation is conserved; that a wash (which removes N E and high K) and EGTA addition (in the presence of the above agents) produce similar effects on force (i.e. relaxation), but a t very different Ca;+ levels (FIGS. 1 and 2); and that ionophore-induced contractions require much higher levels of CaT+ than N E and high K to produce the same amount of force. NE-induced contractions in Ca-free media have been attributed to intracellular