Low temperature blocks the stimulatory effect of human chorionic gonadotropin on steroidogenic acute regulatory protein mRNA and testosterone production but not cyclic adenosine monophosphate in mouse Leydig tumor cells.
Low temperatures slow down metabolism, partly because the kinetic energy of molecules is reduced and enzymes may be structurally impaired. We now report that relative to its maximal activity at 37 degrees C, adenylate cyclase (AC) still retained 25% functionality (determined as cyclic adenosine monophosphate [cAMP] production) at 4 degrees C in mouse Leydig tumor cells (MLTC-1) in response to 50 IU/L human chorionic gonadotropin (hCG), whereas steroidogenic acute regulatory (StAR) protein mRNA and testosterone production were completely impaired. The incubation of MLTC-1 with the phosphodiesterase inhibitor (3-isobutyl-1-methylxanthine; IBMX) resulted in significantly increased intracellular cAMP concentration at all 3 temperatures, but this had no impact on testosterone production. AC, cAMP, and phosphodiesterase form an important intracellular second-messenger mechanism in many organisms, some that inhabit very low temperature niches. The cold-resistance of AC and phosphodiesterase may thus have evolved to cope with adverse conditions. Although hibernation may lead to decreased steroid hormone production, it is also likely that cold-mediated decreased steroid hormone production induces hibernation.
Department of Chemical Pathology, The Chinese University of Hong Kong, Prince of Wales Hospital, Shatin.
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D015056:1-Methyl-3-isobutylxanthine / Q000494:pharmacology; D000262:Adenylyl Cyclases / Q000378:metabolism; D000818:Animals; D002460:Cell Line; D006063:Chorionic Gonadotropin / Q000494:pharmacology*; D003080:Cold Temperature; D006224:Cricetinae; D000242:Cyclic AMP / Q000096:biosynthesis*; D006801:Humans; D007984:Leydig Cell Tumor / Q000378:metabolism*; D008297:Male; D008647:Mesocricetus; D051379:Mice; D010726:Phosphodiesterase Inhibitors / Q000494:pharmacology; D010750:Phosphoproteins / Q000096:biosynthesis*; D012333:RNA, Messenger / Q000096:biosynthesis*; D020133:Reverse Transcriptase Polymerase Chain Reaction; D013736:Testicular Neoplasms / Q000378:metabolism*; D013739:Testosterone / Q000096:biosynthesis*; D000098682:Steroidogenic Acute Regulatory Protein
D006063:Chorionic Gonadotropin; D010726:Phosphodiesterase Inhibitors; D010750:Phosphoproteins; D012333:RNA, Messenger; D000098682:Steroidogenic Acute Regulatory Protein; D013739:Testosterone; D000242:Cyclic AMP; D000262:Adenylyl Cyclases; D015056:1-Methyl-3-isobutylxanthine