Lack of circadian rhythm of plasma concentrations of vasoactive intestinal peptide in patients with orthotopic heart transplants

Effects of enalapril on vasoactive intestinal peptide metabolism and tissue levels

Angiotensin converting enzyme inhibitor therapy results in an increase in cardiac output without an increase in heart rate suggesting a positive inotropic effect. This cannot be explained by changes in angiotensin II and bradykinin concentrations. Angiotensin converting enzyme may also metabolise vasoactive intestinal peptide (VIP), a vasodilator and positive inotrope whose concentration in the heart declines in heart failure. We sought to determine whether changes in plasma VIP or its metabolism might explain the positive inotropic effect of angiotensin converting enzyme inhibitors. We also measured VIP in the heart to determine whether a local increase in VIP might explain this effect. Male Sprague-Dawley rats were randomised to control and enalapril groups (2 mg kg(-1) day(-1)). After 7 days, rats were anaesthetised and underwent metabolic clearance studies for VIP or had hearts, lungs and kidneys removed and snap frozen. VIP concentrations in plasma, infusate and tissue extracts were measured by radioimmunoassay. Plasma concentrations of VIP were unchanged by treatment with enalapril (control: 7.7 +/- 0.8 pmol l(-1); enalapril: 7.9 +/- 0.8 pmol l(-1) ), while the metabolic clearance rate of) VIP increased significantly (control: 10.4 +/- 1.4 ml min(-1) 100 g(-1); enalapril: 17.3 +/- 1.6 ml min(-1) 100 g(-1); p < 0.005). Secretion rate) also increased in enalapril treated rats (139.1 +/- 25.0 pmol min(-1) 100 g(-1) compared with controls (96.3 +/- 13.4 pmol min (-1) 100 g(-1); P< 0.01). VIP in the heart increased after enalapril (control: 208.4 +/- 39.0 pmol g (-1); enalapril: 928.9 +/- 123.6 fmol g(-1); P < 0.0005). Angiotensin converting enzyme inhibition increases the metabolism of VIP. However, the significant increase in the myocardial concentration of VIP may contribute to the beneficial haemodynamic inotrope effects of angiotensin converting enzyme inhibitors.

Diurnal changes in cyclosporine effect on ornithine decarboxylase and noradrenergic and cholinergic activities in submaxillary lymph nodes

Diurnal changes in cyclosporine efficacy to affect ornithine decarboxylase activity, [3H]norepinephrine uptake and [3H]choline conversion into [3H]acetylcholine were examined in rat submaxillary lymph nodes. Cyclosporine (5 or 20 mg/kg) caused a dose-dependent decrease in lymph node ornithine decarboxylase, being active at 5 or 20 mg/kg in Freund's adjuvant-treated rats, and at 20 mg/kg in rats treated with the adjuvant's vehicle. In immunized rats the lower cyclosporine dose was ineffective when injected during the night. Cyclosporine increased lymph node [3H]norepinephrine uptake dose dependently, with significant differences between the 20 mg/kg dose and controls in vehicle-treated rats and between 5 or 20 mg/kg and controls in Freund's adjuvant-treated rats. In immunized rats, 5 mg/kg cyclosporine increased [3H]norepinephrine uptake when injected at 13:00 or 17:00 h. Both doses of cyclosporine augmented lymph node synthesis of [3H]acetylcholine to a similar extent. In immunized and non-immunized rats cyclosporine suppressed the diurnal rhythm of lymph node adrenergic and cholinergic activity found in controls. After unilateral sympathetic denervation (by superior cervical ganglionectomy) and/or unilateral parasympathetic decentralization (by chorda tympani section), cyclosporine (5 mg/kg) decreased Freund's adjuvant-induced activation of lymph node ornithine decarboxylase when injected at 17:00 or 01:00 h. On the sham-operated side, cyclosporine was effective when injected at 17:00 h only. Decentralization, or a combined ganglionectomy plus decentralization, decreased lymph node ornithine decarboxylase activity. The results active regulation of the effects of cyclosporine in submaxillary lymph nodes by local autonomic nerves.

Long term effects of ritodrine on blood pressure and heart rate of adolescents exposed during the prenatal stage

OBJECTIVE

To determine the long term cardiovascular effects in adolescents exposed to ritodrine during prenatal stage.

STUDY DESIGN

Twenty-seven ritodrine-exposed subjects and 19 controls, of both sexes, clinically healthy, and born at normal term, were evaluated for systolic blood pressure (SBP), diastolic blood pressure (DBP) and heart rate (HR) each during 48 hours, with a Colin Ambulatory monitor. Data analysis were performed by individual Cosinor method, and non-parametric Mann Whitney's test and Lamotte procedures.

RESULTS

Adolescents who were exposed to ritodrine showed losses in the HR rhythm and rising middle pulse values. Although SBP and DBP rhythm remains constant, the increase of maximum and minimum values for SBP as well as a rise of maximal rates of DBP suggest a possible hypertensive effect mediated by beta mimetic exposure.

CONCLUSION

This study suggests a hypertensive effect mediated by beta mimetic exposure.