Interactions between atrial natriuretic factor (ANF) and thyrotropin or somatostatin in their effects on thyroid growth processes; studies in vitro and ex vivo in vitro.

The goal of our present study has been to examine the effects of the atrial natriuretic factor (ANF) on the growth processes in rat thyroid lobes. In the initial in vitro experiment, thyroid lobes were preincubated with rat ANF (Sigma) for 30 min in RPMI 1640 medium with 3H-thymidine (2 microCi/ml), and later on 15% fetal calf serum (FCS), Hepes buffer and the remaining tested substances [TSH 20 mIU/ml, somatostatin (SS) 10(-7)M] were added. Preincubations with ANF were not conducted in the controls and in the group exposed to TSH alone. Incubations of all the examined groups (controls, TSH alone, ANF alone, ANF together with TSH or ANF together with SS) with 3H-thymidine were carried out for 4 hours. We obtained the following results: at none of the examined concentrations (10(-5)M, 10(-7)M, 10(-9)M), did ANF significantly affect the rate of 3H-thymidine incorporation in vitro. Neither did TSH alone nor ANF with TSH jointly significantly influence the process in question. However, we observed increased rates of the 3H-thymidine uptake, following the joint exposure of thyroid lobes to ANF (10(-7)M or 10(-9)M) and SS (10(-7)M), when compared to ANF alone. In the ex vivo in vitro experiment, direct intrathyroidal microinjections of ANF alone or jointly with TSH or SS, were carried out. Twenty four (24) hours after the microinjections, all the animals were sacrificed by decapitation, the thyroid lobes being collected and incubated for 4 hours with 3H-thymidine (2 microCi/ml).(ABSTRACT TRUNCATED AT 250 WORDS)