Thyrotropin (TSH), long-acting thyroid stimulator (LATS), and dibutyryl cyclic- AMP (DBcAMP) markedly stimulated intracellular colloid droplet formation (endocytosis) in canine thyroid slices. The addition of chlorpromazine (Cpz) or propranolol (Ppl) to the incubation medium inhibited or completely eliminated the response to each of the 2 stimulators. Isoproterenol did not induce endocytosis, nor did it potentiate the endocytotic effect of TSH. Cpz (2×10-4M) or Ppl (5×10-4M) also blocked TSH-induced or LATS-induced stimulation of the oxidation of glucose-l-14C to 14CO2. This concentration of Cpz also inhibited TSH-induced 32P incorporation into thyroid slice phospholipid, although causing mild stimulation of this process by itself. Ppl alone (5×10-4m) produced marked stimulation of phospholipogenesis; in lower concentration (10-4M) it caused mild stimulation and, when combined with TSH, it was neither fully additive nor inhibitory. These studies are interpreted as evidence that Ppl, chosen for study as an...
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Onaya et al. (1969) studied this question.