To explore the adrenocortical function at low temperatures, the time-dependent transition of corticoidogenesis (CG) as well as the effect of verapamil, a Ca²⁺ channel blocker, on CG were examined at 27°C using primary cultured bovine adrenocortical cells.
CG was induced using adrenocorticotropic hormone (ACTH, 10pM to 1μM), which stimulates the receptor-operated Ca²⁺ channel and adenylate cyclase activity; dibutyryl cyclic AMP (db-cAMP, 0.25 to 4mM), which mimics the intracellular action of cyclic AMP; and 30mM K⁺, which activates the voltage-dependent Ca²⁺ channel. Cells were incubated together with each of these secretaogues for 3 hours at 27°C.
Though the CG induced by 1nM ACTH-and 1mM db-cAMP increased for 3 hours at 27°C in the presence of 1.2mM Ca²⁺, the CG induced by 30mM K⁺ did not show any increase after 2 hours.
Both 5μM and 10μM of verapamil inhibited the CG induced by 10pM ACTH dose-dependently at 37°C. However, 5μM of verapamil showed no inhibiting effect at 27°C. Even 10μM verapamil did not influence the CG induced by 1mM db-cAMP.
In the absence of extracellular Ca²⁺, 10μM verapamil did not influence the CG induced by ACTH (10nM to 1μM) or db-cAMP (0.25 to 4mM) at 27°C.
These experiment results show that the functions of adrenocortical cells are kept effective for 3 hours and that Ca²⁺ is also important for CG at 27°C. Although it is well known that the increases in both cyclic AMP and intracellular Ca²⁺ are essential for the CG induced by various stimulants at 37°C, it is suggested that cyclic AMP plays a more important roll in CG than Ca²⁺ does at low temperatures.

To study the adrenocortical function in fever, we examined the effect of high temperatures on the corticoidogenesis (CG) in isolated bovine adrenocortical cells. To evoke CG, a stimulus was given using adrenocorticotropic hormone (ACTH, 1pM to 10nM), which stimulates the receptor operated Ca²⁺ channel (ROC) and adenylate cyclase activity; dibutyryl cyclic AMP (db-cAMP, 1mM), which mimics intracellular action of cyclic AMP; and high (30mM) K⁺, which activates the voltage dependent Ca²⁺ channel (VDC). Cells were incubated for 1 hour with each of the above mentioned secretaogues at 37°C, 40°C, and 42°C (only for ACTH). Compared with incubation at 37°C, the log dose response curve of ACTH shifted to the right, the maximal effect decreased to about 60% at 40°C, and CG ceased at 42°C. The use of Ca²⁺ (1.2mM) alone evoked CG via the nonspecific Ca²⁺ channel (NSC) at 37°C, but not at 40°C. 30mM K⁺-induced CG decreased to below 50% at 40°C, but 1mM db-cAMP-induced CG decreased only to 80%. However, the conversion of 25-hydroxycholesterol to corticoid was not affected at 40°C
The results of these experiments show that VDC and NSC are not the main factors of CG at 40°C and that the enzyme activity beyond the side chain cleavage of cholesterol is not affected. Since the increases in cyclic AMP production and intracellular Ca²⁺ are essential in various stimulants-induced CGs, it is suggested that adenylate cyclase and ROC play a more important role in CG at 40°C than VDC and NSC.

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.
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.

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.
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.
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.