Peripheral metabolism and secretion rate of thyrotropin in streptozotocin-diabetic rats.

Abstract

The MCR and secretion rate of rat TSH have been measured to determine whether altered rates of TSH metabolism could account for the lower plasma TSH concentration in streptozotocin-diabetic rats. The MCR of TSH in diabetics, (0.57 ± 0.04 ml/min) was similar to that of control animals (0.55 ± 0.08 ml/min). So was the t.A (19.5 ± 0.6 min) for controls and (20.0 ± 0.8 min) for diabetics. The secretion rate in controls (0.17 ± 0.01 μg/min) was higher than in diabetic rats (0.10 ± 0.01 Mg/min) (P < 0.01). Furthermore, plasma TSH concentration was measured before and after an iv injection of 50 or 100 ng of TRH. The basal plasma TSH levels in diabetic rats (0.26 ± 0.07 μg/ml) w e r e lower than those in control rats (0.40 ± 0.09 μg/ml). The maximal TSH response to 50 ng TRH in diabetics (0.60 ± 0.10 μg/ml) w a s significantly lower than that in the control group (1.2 ± 0.15 μg/ml; P < 0.01). Similar differences in response of the two groups were found in the plasma TSH concentrations after 100 ng TRH (1.75 ± 0....