Plasma Renin Activity and in vitro Synthesis of Aldosterone by the Adrenal Glands of Rats with Spontaneous, Renal, or Pinealectomy‐Induced Hypertension

Abstract

In the present study a comparison was made on the role of the renin-aldosterone system in rats with various forms of experimental hypertension (pinealectomy-induced, renal and spontaneous). The plasma sodium and potassium concentrations as well as renin activity were measured. The in vitro production of aldosterone by quartered adrenal glands of these rats was also determined. 5 weeks after the operations the blood pressure of the pinealectomized and renal operated rats was significantly increased. The plasma sodium concentration did not differ in various groups, but that of potassium was decreased in the renal hypertensive animals. The plasma renin activity of the pinealectomized rats was elevated while in other forms of hypertension it was at the control level. The basal aldosterone production by the adrenal quarters was equal in all the groups. ACTH, dibutyryl cyclic adenosine-3',5'-monophosphate (DBA) and 5HT stimulated the aldosterone production. The responses to ACTH and DBA were greater in the adrenals of renal hypertensive rats than in the other forms of hypertension or in the controls. We suggest that the renin-aldosterone system is of importance in the maintenance of renal hypertension, while in pinealectomy-induced hypertension elevated plasma renin activity reflects an increased sympathetic activity which probably is the main cause of hypertension in these animals.

Hypertension and Cardiovascular Remodelling in Rats Exposed to Continuous Light: Protection by ACE-Inhibition and Melatonin

“…Continuous light-induced hypertension development is obviously associated with more complex neurohumoral disequilibrium than with a simple deficit of the melatonin. The plasmatic renin activity was increased five weeks after pinealectomy, possibly reflecting an increased sympathetic tone, a major contributor to hypertension development in pinealectomized animals [57]. Constant illumination was associated with enhanced adrenocorticotropic hormone and corticosterone plasmatic concentrations [58].…”

Melatonin in aging and neurodegeneration

“…The contributive role of melatonin in regulating periferial and cerebral blood flow is well known [Doolen et al, 1998;Ré griny et al, 1998;Yang et al, 2001]. The first indication for melatonin's vasoactive properties was the induction of hypertension in pinealectomized rats [Karppanen et al, 1975]. Melatonin mediates both contractile and relaxant effects in arteries in a concentration-dependent manner [Doolen et al, 1998].…”

Melatonin reduces disseminate neuronal death after mild focal ischemia in mice via inhibition of caspase‐3 and is suitable as an add‐on treatment to tissue‐plasminogen activator

“…Brain protection is independent of hemodynamic changes and involves inhibition of caspase-3. arterial blood pressure [19][20][21] and either constricts or dilates blood vessels in a concentration-dependent manner [22,23]. In transient focal ischemia, it was previously shown in rats that melatonin increases cerebral laser Doppler flow (LDF) after tissue reperfusion [6].…”