Key result
Telmisartan normalizes fluid intake and vasopressin without altering plasma osmolality in heat-exposed, high-salt rats.
Why the study?
Plasma osmolality and neurohumoral signals play important roles in cardiovascular pathophysiology, prompting investigation into the effect of high environmental temperature on these responses in salt-loaded rats with and without angiotensin receptor blockade.
Does telmisartan alter plasma osmolality and neurohumoral responses in rats exposed to high environmental temperature and a high salt diet?
Does telmisartan alter plasma osmolality and neurohumoral responses in rats exposed to high environmental temperature and a high salt diet?
In a rat model, angiotensin II receptor blockade with telmisartan failed to reverse hyperosmolality induced by high salt diet and heat exposure, though it modulated fluid intake and specific neurohumoral responses.
Plasma osmolality (pOsmol) and neurohumoral signals play important roles in the pathophysiology of cardiovascular diseases. Our study investigated the effect of high environmental temperature (HET) on neurohumoral responses and pOsmol in rats fed a high salt diet (HSD), with and without angiotensin II receptor blockade (ARB), using telmisartan. Fifty-six male 8-week old Sprague-Dawley rats (95-110g) were randomly assigned into seven groups of 8 rats. These included control rats (I) fed with 0.3% NaCl diet (normal diet, ND); salt-loaded rats (II) fed with 8% NaCl (high salt) diet; ND rats (III) exposed to HET (38.5±0.5oC ) 4 hours daily per week; rats (IV) fed with 8% NaCl diet and exposed to HET daily. Others included rats (V) fed with 8% NaCl diet and treated with telmisartan (30mg/kg); ND rats (VI) exposed to HET and treated with telmisartan; rats (VI) fed with 8% NaCl diet, exposed to HET and treated with telmisartan. Plasma angiotensin II, aldosterone, vasopressin and norepinephrine (NE) concentrations were determined by ELISA technique; pOsmol from plasma K+, Na+ and Urea. HSD combined with HET in rats synergistically increased pOsmol (P<0.001) with an associated non-synergistic rise in fluid intake (P<0.001), fluid balance (P<0.001), plasma angiotensin II (P<0.01) and aldosterone (P<0.05), NE (P<0.001) and vasopressin (P<0.05) concentrations compared to control. Telmisartan did not alter pOsmol in all the treated-rats, but normalized fluid intake levels and plasma vasopressin in the rats exposed to either HSD or HEt alone. Prolonged exposure of rats to hot environment exacerbated the effect of excess dietary salt on pOsmol, with no effect on angiotensin II-mediated neurohumoral responses.
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Agbaraolorunpo et al. (2021) studied High salt diet and high environmental temperature exposure (n=56). Telmisartan vs. Control (normal diet, room temperature) was evaluated on Plasma osmolality (p=<0.001). In rats fed a high salt diet and exposed to high environmental temperature, telmisartan did not alter the synergistically increased plasma osmolality but normalized fluid intake and plasma vasopressin.
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