Effects of Growth Hormone and Estrogen on Rat Angiotensinogen Quantified by an Enzyme Linked Immunosorbent Assay

Effect of castration on renin-angiotensin system of hypertensive rats submitted to chronic hypobaric hypoxia (simulated altitude: 4400 m)

The aim of the present study was to provide an overview of the role of circulating gonadal steroids on the adaptive changes of the renin-angiotensin system to chronic hypobaric hypoxia (CHH: 4400 m simulated altitude in an hypobaric chamber) and the development of experimental hypertension by bilateral renal ischemia. In order to fulfill this goal, blood pressure (BP), plasma renin activity (PRA) and plasma angiotensinogen concentration (PAoC) as well as haematocrit (Htc) and body weight (BW) of intact and post-puberal castrated normotensive (Nt) and hypertensive (Ht) rats of both sexes were studied following an experimental design similar to that of previous works. Post-puberal castration decreased BP of Nt and Ht rats subjected to CHH. Sexual dimorphism in BP, PRA and PAoC was maintained while that in haematocrit disappeared after castration. Results suggest that circulating sexual steroid hormones are involved in the response of the renin-angiotensin system to the experimental conditions of environmental reduced O2 partial pressure.

Changes in the renin-angiotensin-aldosterone system in 2 kidney -2 clip Goldblatt hypertensive rats of both sexes submitted to chronic hypobaric hypoxia

The effect of chronic hypobaric hypoxia (CHH) on the development of 2k-2c Goldblatt renovascular hypertension has been analyzed in rats of both sexes. Results have shown lower values of blood pressure (BP) in all the animals exposed to CHH compared with their normoxic control (P < 0.001). Haematocrit was increased by adaptation to CHH (P < 0.001), and was larger in male than in female hypoxic rats, both normotensive (P < 0.05) and hypertensive (P < 0.01). Plasma renin activity was higher in normoxic and hypoxic hypertensive female rats than in their normotensive controls (P < 0.05). Plasma angiotensinogen concentration was higher in normoxic control male rats than in all the other groups. This difference disappeared after adaptation to CHH or development of hypertension. Plasma aldosterone concentration was lowest in normoxic control male rats and the difference also disappeared after CHH or renal ischemia. Present data indicate that CHH blunts the hypertensive response to bilateral renal ischemia in male and female rats. Sexual differences related to the mechanisms that could be involved in hypertension development have been observed. The renin-angiotensin-aldosterone system might be modulated by gonadal hormones during the development of hypertension.