Rambotti M G, Mughetti D, Spreca A
Department of Experimental Medicine and Biochemical Sciences, University of Perugia, Italy.
Brain Res. 1994 Apr 25;644(1):52-8. doi: 10.1016/0006-8993(94)90346-8.
We investigated the ultracytochemical localization of particulate guanylate cyclase (GC) in the rat neurohypophysis after activation with rat atrial natriuretic factor (rANF) or porcine brain natriuretic peptide (pBNP). Under our experimental conditions, the presence of GC reaction product indicated that rANF and pBNP were strong activators of particulate GC since samples incubated in basal conditions without rANF or pBNP did not reveal any GC reaction product. The rANF-stimulated GC was localized both to pituicytes and to nerve fibers and endings whereas the pBNP-stimulated GC was present exclusively in nerve fibers and endings. Recently, two subtypes of receptors for natriuretic peptides have been identified as two isoforms of particulate GC [24,50]. Our data indicate that the receptors of the two hormones have a partially distinct distribution in the rat neurohypophysis. In pituicytes, GC reaction product was found on plasma membrane of finger-like processes and on the membranes surrounding the lipid droplets. In nerve fibers and endings, GC reaction product was associated with intracellular membranes. This finding suggests that the enzyme could mediate an internal inhibitory action of these hormones on the release of vasopressin and oxytocin.
我们研究了用大鼠心房利钠因子（rANF）或猪脑利钠肽（pBNP）激活后大鼠神经垂体中颗粒型鸟苷酸环化酶（GC）的超微细胞化学定位。在我们的实验条件下，GC反应产物的存在表明rANF和pBNP是颗粒型GC的强激活剂，因为在没有rANF或pBNP的基础条件下孵育的样本未显示任何GC反应产物。rANF刺激的GC定位于垂体细胞以及神经纤维和终末，而pBNP刺激的GC仅存在于神经纤维和终末。最近，利钠肽的两种受体亚型已被鉴定为颗粒型GC的两种同工型[24,50]。我们的数据表明，这两种激素的受体在大鼠神经垂体中的分布部分不同。在垂体细胞中，GC反应产物出现在指状突起的质膜和围绕脂滴的膜上。在神经纤维和终末，GC反应产物与细胞内膜相关。这一发现表明，该酶可能介导这些激素对血管加压素和催产素释放的一种内在抑制作用。
