Adrenocortical Function during Hypothermia. (No.2). Inhibitory effect of low temperature on corticoidogenesis in isolated bovine adrenocortical cells / 日本温泉気候物理医学会雑誌

Effects of low temperature on corticoidogenesis (CG) were studied in isolated bovine adrenocortical cells. In the presence of Ca²⁺, cells were incubated with adrenocorticotropic hormone (ACTH) at 27°C and 37°C for 1 hour. After the incubation, the amount of corticoid was measured fluorometrically. After the incubation at 27°C, as compared with that at 37°C, the CGs induced by 10pM and 1nM ACTH decreased, but the CG induced by 10nM ACTH was not affected. Even in the absence of extracellular Ca²⁺, 10nM ACTH could induce the same degree of CGs at 37°C and 27°C, There was no difference in the amount of conversion of 25-hydroxycholesterol to corticoid between the incubations at 37°C and 27°C. The amount of conversion at 20°C, however, was significantly lower.<br>Our study shows that Ca²⁺ is not an important second messenger for CG at 27°C, and that the enzyme activity beyond side chain cleavage of cholesterol (SCC) does not diminish.<br>Because cyclic AMP and Ca²⁺ are known as second messengers of ACTH, it is suggested that cyclic AMP plays a more important role than Ca²⁺ in CG during hypothermia and that ACTH not only stimulates SCC but also activates enzyme (s) beyond SCC to evoke CG in the case of deep hypothermia.

Adrenocortical Function during Hypothermia. Effect of low temperature on the corticoidogenesis in cultured bovine adrenocortical cells / 日本温泉気候物理医学会雑誌

Effects of hypothermia on corticoidogenesis (CG) were investigated in primary cultured bovine adrenocortical cells. In order to evoke CG, adrenocorticotropic hormone (ACTH), dibutyryl cyclic AMP (db-cAMP), and high K⁺ were used. In the presence of the above mentioned secretagogues, cells were incubated at 37°C, 27°C, and 20°C for 1 hour. Although there was no difference between the ACTH-induced CGs at 37°C and 27°C, CG was significantly lower at 20°C. Both db-cAMP and high K⁺-induced CGs were significantly lower at 27°C, and were not observed at 20°C.<br>These results indicate that CG is not affected by moderate hypothermia, and is not eliminated even by deep hypothermia. It is also suggested that ACTH influences not only adenylate cyclase and Ca²⁺ channels, but also various processes of glucocorticoid production and could evoke CG at 20°C in bovine adrenocortical cells.