Rubio A, Guerrero J M, Reiter R J, Osuna C
Department of Medical Biochemistry and Molecular Biology, University of Seville School of Medicine, Spain.
Endocrinology. 1993 Jan;132(1):393-8. doi: 10.1210/endo.132.1.8380384.
The regulation by alpha- and beta-adrenergic receptor agonists of rat pineal N-acetyltransferase (NAT) activity during development was studied. We found that isoproterenol, a beta-adrenergic agonist, exhibited a weak stimulatory effect on pineal NAT activity during the first 3 weeks of age. Indeed, the drug did not mimic the effect of darkness on pineal NAT activity until the fourth week of age. The results might be explained by the existence of other mechanisms, in addition to those that involve beta-adrenergic receptors, which regulate pineal NAT activity during early postnatal development. In line with this, we determined that phenylephrine, an alpha 1-adrenergic agonist, stimulated NAT activity during both the day and at night in 2-week-old rats, while exhibiting no effect in adult rats. Methoxamine, an alpha 1-adrenergic agonist more selective than phenylephrine, also activated NAT activity in young, but not in adult, rats. Moreover, prazosin, a selective alpha 1-adrenergic receptor blocker, prevented pineal NAT activation by norepinephrine or darkness at night in 2-week-old rats, but not in adult animals. The results suggest that alpha 1-adrenergic receptors may be more important than beta-adrenergic receptors in regulating rat pineal NAT activity during development.
研究了α-和β-肾上腺素能受体激动剂对大鼠松果体N-乙酰转移酶（NAT）活性在发育过程中的调节作用。我们发现，β-肾上腺素能激动剂异丙肾上腺素在出生后的前3周对松果体NAT活性表现出微弱的刺激作用。实际上，该药物直到第4周龄才模拟黑暗对松果体NAT活性的影响。这些结果可能是由于除了涉及β-肾上腺素能受体的机制外，还存在其他机制，这些机制在出生后早期发育过程中调节松果体NAT活性。与此一致的是，我们确定α1-肾上腺素能激动剂去氧肾上腺素在2周龄大鼠的白天和夜间均刺激NAT活性，而在成年大鼠中无作用。甲氧明是一种比去氧肾上腺素更具选择性的α1-肾上腺素能激动剂，也能激活幼龄大鼠而非成年大鼠的NAT活性。此外，选择性α1-肾上腺素能受体阻滞剂哌唑嗪可阻止2周龄大鼠夜间去甲肾上腺素或黑暗引起的松果体NAT激活，但对成年动物无此作用。结果表明，在发育过程中，α1-肾上腺素能受体在调节大鼠松果体NAT活性方面可能比β-肾上腺素能受体更重要。
