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 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.