Kodjo M K, Leboulenger F, Porcedda P, Lamacz M, Conlon J M, Pelletier G, Vaudry H
European Institute for Peptide Research, INSERM U-413, UA CNRS, University of Rouen, Mont-Saint-Aignan, France.
Endocrinology. 1995 Aug;136(8):3253-9. doi: 10.1210/endo.136.8.7628358.
The adrenal gland of the frog is innervated by a network of fibers containing two tachykinins (ranakinin and [Leu3,Ile7]neurokinin A), which both stimulate corticosteroid secretion from frog adrenal tissue. The aim of the present study was to determine the mode of action of tachykinins on the frog adrenal gland. Double immunolabeling of tissue sections with a monoclonal antibody to tyrosine hydroxylase and an antiserum to substance P showed that tachykinin-containing fibers are preferentially apposed onto chromaffin cells. Immunocytochemical labeling at the electron microscope level revealed that tachykinin-immunoreactive fibers establish close contacts only with adrenochromaffin cells. Ranakinin stimulated corticosterone and aldosterone secretion from perifused adrenal slices, but had no stimulative effect on dispersed adrenal cells. Cytoautoradiographic labeling of frog adrenal cells in primary culture with [3H]substance P revealed the existence of specific binding sites located exclusively on chromaffin cells. Microfluorimetric measurement of cytosolic calcium concentrations ([Ca2+]i) in cultured adrenal cells showed that ranakinin induced a dose-dependent increase in [Ca2+]i in chromaffin cells (ED50 = 2 x 10(-7) M). In contrast, ranakinin did not affect [Ca2+]i in adrenocortical cells. The present results indicate that in the frog adrenal gland, tachykinin-containing fibers make preferential contacts with chromaffin cells, and tachykinins directly activate chromaffin cells. These data suggest that the stimulative effect of tachykinins on corticosteroid secretion is mediated via presynaptic activation of adrenochromaffin cells.
青蛙的肾上腺由含有两种速激肽（蛙激肽和[亮氨酸³，异亮氨酸⁷]神经激肽A）的纤维网络支配，这两种速激肽均能刺激青蛙肾上腺组织分泌皮质类固醇。本研究的目的是确定速激肽对青蛙肾上腺的作用方式。用酪氨酸羟化酶单克隆抗体和P物质抗血清对组织切片进行双重免疫标记显示，含速激肽的纤维优先附着在嗜铬细胞上。电子显微镜水平的免疫细胞化学标记显示，速激肽免疫反应性纤维仅与肾上腺嗜铬细胞建立紧密接触。蛙激肽刺激了灌流肾上腺切片中皮质酮和醛固酮的分泌，但对分散的肾上腺细胞没有刺激作用。用[³H]P物质对原代培养的青蛙肾上腺细胞进行细胞放射自显影标记，发现特异性结合位点仅存在于嗜铬细胞上。对培养的肾上腺细胞胞质钙浓度（[Ca²⁺]i）的微量荧光测定表明，蛙激肽在嗜铬细胞中诱导[Ca²⁺]i呈剂量依赖性增加（半数有效剂量=2×10⁻⁷M）。相反，蛙激肽对肾上腺皮质细胞中的[Ca²⁺]i没有影响。目前的结果表明，在青蛙肾上腺中，含速激肽的纤维优先与嗜铬细胞接触，速激肽直接激活嗜铬细胞。这些数据表明，速激肽对皮质类固醇分泌的刺激作用是通过肾上腺嗜铬细胞的突触前激活介导的。
