Effects of extract from Clerodendron trichotomum on blood pressure and renal function in rats and dogs.

Clerodendron trichotomum Thunb. is a herb which has been used for treatment of hypertension in Chinese medicine. To assess the action of the herb on blood pressure and renal function, the extract was administered to rats and dogs. Intravenous administration of the extract elicited renal vasodilation and increased urine flow and urinary sodium excretion. Acute oral administration of the extract reduced blood pressure of spontaneously hypertensive rats but not of normotensive control rats. Chronic daily administration for 6 weeks prevented the increase in blood pressure of spontaneously hypertensive rats. These results may give some support to the claim on the clinical efficacy of the extract of Clerodendron trichotomum Thunb.

Effect of calcium on prostaglandin E2 release in dogs.

Prostaglandin E2 (PGE2) concentration in arterial and renal venous plasma was determined by radioimmunoassay in anesthetized dogs, and the PGE2 secretion rate was calculated. Intrarenal arterial infusion of CaCl2 (0.68 meq/min) resulted in a biphasic effect on renal blood flow (RBF) and an initial increase followed by a gradual decrease below the preinfusion level. PGE2 secretion rate increased from 7.2 +/- 4.4 to 95 +/- 28 ng/min, with a marked increase of RBF after 3 min of CaCl2 infusion. An equivalent amount of NaCl infused into the renal artery did not affect either the RBF or the PGE2 secretion rate. One-tenth the dose of CaCl2 (0.068 meq/min) infused into the renal artery did not increase either RBF or PGE2 secretin rate, and the RBF gradually decreased after infusion. The transient renal vasodilation observed during infusion of a high dose of CaCl2 ceased with the combined intrarenal infusion of verapamil (100 micrograms/min), and was also abolished by pretreatment with indomethacin (5 mg/kg i.v.). Infusion of CaCl2 (0.68 meq/min) into the femoral artery did not enhance the PGE2 secretion rate from the hindlimb, and femoral blood flow decreased immediately after the infusion. These results suggest tht the renal vessels as well as other resistance vessels are essentially constricted by calcium and that endogenous PGE2 released by calcium may modify this renal vasoconstriction.

Acute sino-aortic denervation in rats produces a selective increase of adrenaline turnover in the dorsal midline area of the caudal medulla oblongata and a reduction of adrenaline levels in the anterior and posterior hypothalamus.

Acute sino-aortic denervation produces an acute reduction of adrenaline stores in the anterior and posterior hypothalamus and a reduction of noradrenaline stores in the dorsal midline area of the caudal medulla oblongata. Furthermore, removal of baroreflex afferents results in an increase of adrenaline turnover in the DCMO but not in the hypothalamus. The present findings give evidence for participation of adrenergic mechanisms in central baroreflex regulation. The findings can be interpreted according to the adrenaline vasodepressor hypothesis of hypertension.