White B H, Mosher K, Binkley S
Endocrinology. 1985 Sep;117(3):1050-6. doi: 10.1210/endo-117-3-1050.
Rat pineal N-acetyltransferase activity (NAT) has a circadian rhythm, with a peak in the dark time. The rhythm of NAT was studied in young rats (26-40 days old). In particular, the possibility of maintenance of prolonged low NAT or prolonged high NAT was studied. NAT (given in nanomoles per pineal gland/h) had peak activity (33.0) in the dark time. Forty-eight hours of constant light suppressed the peak and maintained low NAT (0.5 or less). In vivo, in constant light, NAT was stimulated (to 13.1-29.4) by single injections of isoproterenol. Similarly, NAT was stimulated by isoproterenol or (Bu)2cAMP in vitro. In vivo, multiple injections of isoproterenol stimulated NAT for 14 h (to peak 31.9), but NAT was exhausted and fell to less than 5 over the next 8 h. Similarly, isoproterenol and (Bu)2cAMP exhausted NAT in vitro. High NAT was not maintained. NAT recovered [could be restimulated by dark in vivo, isoproterenol in vivo or in vitro, or (Bu)2cAMP in vitro]. Exhaustion was not permanent. Light can keep NAT at low levels, but dark cannot maintain peak NAT beyond 14 h. The results are interpreted as meaning that the duration of NAT is fixed.
大鼠松果体N - 乙酰基转移酶活性（NAT）具有昼夜节律，在黑暗时段达到峰值。研究了幼鼠（26 - 40日龄）的NAT节律。特别研究了维持长时间低NAT或长时间高NAT的可能性。NAT（以每松果体纳摩尔数/小时表示）在黑暗时段具有峰值活性（33.0）。持续光照48小时会抑制峰值并维持低NAT水平（0.5或更低）。在体内，在持续光照下，单次注射异丙肾上腺素可刺激NAT（至13.1 - 29.4）。同样，在体外，异丙肾上腺素或（Bu）2cAMP可刺激NAT。在体内，多次注射异丙肾上腺素刺激NAT达14小时（至峰值31.9），但在接下来的8小时内NAT耗尽并降至5以下。同样，在体外，异丙肾上腺素和（Bu）2cAMP使NAT耗尽。高NAT水平无法维持。NAT可恢复（在体内可被黑暗重新刺激，在体内或体外可被异丙肾上腺素刺激，在体外可被（Bu）2cAMP刺激）。耗尽并非永久性的。光照可使NAT保持在低水平，但黑暗无法使NAT峰值维持超过14小时。结果被解释为意味着NAT的持续时间是固定的。
