Effects of acute hypotension and hypertension on serum TSH concentrations in male rats.

The effect of acute hypertension and hypotension on serum TSH concentration was studied in anesthetized male rats. I.v. infusions (10 and 30 min) of Na-nitroprusside and dihydralazine induced a profound hypotension, and angiotensin amide and noradrenaline increased blood pressure, but none of the treatments significantly modified serum TSH concentrations. Also clonidine and noradrenaline, when given i.p., caused hypertension, but again the increase of serum TSH levels was not consistent. When the whole material was analysed, there was a scarcely significant correlation between the change of blood pressure and the change of serum TSH level. It is inferred that the drugs affecting TSH secretion, do not exert their action solely by changing the blood pressure.