Renal function and pituitary hormone release during cerebral osmostimulation and TRH in dogs

The effects of increases in serum osmolality on renal function and plasma levels of radioimmunoassayable prolactin (PRL) and luteinizing hormone (LH) were examined during intracarotid (IC) infusions of hypertonic NaCl in conscious dogs with a sustained water diuresis (SWD). A 10 minute bilateral IC infusion of 45 mumole/kg X min X artery of NaCl during SWD which raised jugular osmolality by 10.1 mOsm/kg, without significantly altering peripheral venous osmolality, produced a significant decrease in free water clearance (CH2O) at 20 to 40 minutes postinfusion. IC infusions of 0.9% NaCl did not produce an antidiuretic response. No change in heart rate or blood pressure from preinfusion control values occurred during NaCl infusions. Elevations in cerebral osmolality did not result in changes in circulating levels of LH or PRL which qualitatively differed from levels of these hormones recorded during IC infusions of 0.9% NaCl. Although fluctuations in levels of LH occurred during experiments, renal function was not concomitantly affected. The results suggest that a specificity exists in the hormonal response to selective elevations of cerebral osmolality. The administration of TRH 3.8-4.2 micrograms/kg produced a transient increase in blood pressure and inhibited a water diuresis, the latter possibly as a result of releasing antidiuretic hormone.