Intrinsic GABAergic system of adrenal chromaffin cells.

Abstract

Histochemical and biochemical studies demonstrate that -aminobutyric acid (GABA), glutamic acid de- Chromaffin cells of adrenal medulla specialize in the production, storage, and secretion of catecholamines (CAs). These processes are modulated by nicotinic receptors that are located in chromaffin cell membranes and are innervated by splanchnic cholinergic axons. However, recent evidence has challenged this simplistic view on the neuronal modulation of adrenal medullary function. This evidence includes a documentation of the presence in adrenal medulla of opioid peptides (1-3), substance P (4), somatostatin (5), vasoactive intestinal peptide (6), and histamine (7). Though we know that receptors for opioids (8) and substance P (9) interact with cholinergic receptors, our understanding of the molecular mechanisms operative in the modulation of medullary function is far from being complete. The present report shows that primary cultures of chromaffin cells prepared from bovine adrenal can synthesize, store, release, and inactivate y aminobutyric acid (GABA); moreover, GABA receptors appear to modulate the secretion of CA mediated by acetylcholine (AcCho). The GABA receptors of medulla include a recognition site for benzodiazepines and function in a manner reminiscent of brain GABAergic receptors. MATERIALS AND METHODSCell Preparation. Primary cultures of chromaffin cells were prepared from bovine adrenal glands, obtained at a local slaughterhouse (Treuth and Son, Catonsville, MD), according to Kilpatrick et al. (10) with minor modifications (8). These cultures were maintained with a Dulbecco's modified Eagle medium (DME medium, GIBCO), 5 mM Hepes (pH 7.4), 10% fetal calf serum (GIBCO), 100,000 units of penicillin per liter, 10 mg of streptomycin (GIBCO) per liter, 40 mg of gentamycin (Shering) per liter, 50,000 units of mycostatin (Squibb) per liter, and 5 ,.M fluorodeoxyuridine (Sigma).CA Release. The chromaffin cells were placed in 24-well plastic dishes (Costar). Each well contained -2.5 x 105 cells in 1 ml of DME medium and was kept for 5-7 days at 370C in 5% C02/95% air. The cells were tightly attached to the plastic after 5-7 days in culture. At this time the dishes were placed in a 370C water bath, the DME medium was aspirated, and the cells were washed twice with Locke solution (8) and then were incubated at 370C for 10 min in 500 u1l of Locke solution with or without the drug to be studied. Epinephrine and norepinephrine released in the medium or contained in the cells was measured with an HPLC coupled to electrochemical detection (8).Uptake

The actions of propofol on inhibitory amino acid receptors of bovine adrenomedullary chromaffin cells and rodent central neurones

“…This formulation of propofol (8.4 The molecular mechanism of the propofol-induced potentiation Propofol could potentiate GABA-evoked responses by one of several mechanisms, including an inhibition of GABA uptake by the chromaffin cell (Kataoka et al, 1984), a change in the driving force upon chloride ions which mediate the GABAA response (Cottrell et al, 1985;Peters et al, 1989), an increase in the conductance of GABA-activated single channels, or an increase in the probability of the GABA-channel being in a conducting state. The GABA uptake blocker, nipecotic acid (1 mM), has no effect on GABA-evoked whole-cell currents in bovine chromaffin cells .…”

Pharmacological modulation of adrenal medullary GABAA receptor: consistent with its subunit composition

“…The EC50 values are very similar for this effect on cerebellum or high affinity sites of the cortex and hippocampus (Duggan & Stephenson, 1988). Moreover, KD values of flunitrazepam binding were also of the same order of magnitude as those for high affinity binding sites in brain membranes (10 ± 4 nM, Sigel et al, 1983;2.6 nM, Edgar & Schwartz 1992), purified GABAA receptors (3.0 ± 0.9 nM, Edgar et al, 1992) and in adrenal medulla membranes (4 ± 0.6 nM, Parramon et al, 1994;9.8 nM, Kataoka et al, 1984). These observations lead us to suggest that there is a strong homology between BZ binding site of adrenal medulla and brain structures.…”

“…This is the case with the adrenal medulla, where GABA regulates catecholamine (CA) secretion (Castro et al, 1989). This function is mainly mediated by binding to GABAA receptors (Kataoka et al, 1984;Castro et al, 1988), through a mechanism dependent on the membrane potential (Gonzalez et al, 1992).…”

Localization of GABA, GAD65 and GAD67 in Rat Epiphyseal Growth Plate Chondrocytes.

“…Furthermore, GABA is not confined to the nervous system. GABA has been found in chromaffin cells of the adrenal gland, platelets and erythrocytes of blood, endocrine cells of the gastrointestinal tract, tubular epithelium of the kidney, hepatocytes, ciliated epithelium of the oviduct, B cells and acinar cells of the pancreas, pinealocytes, spermatozoa and keratinocytes [12,14,23,27,34]. GABA in non-neuronal tissues may play a multitude of functions such as regulation of motility and agglutination of spermatozoa, stimulation of testosterone production, regulation of uterotubal and gut motility, and control of hormone release in endocrine cells in the adrenal medulla, pancreas and gastrointestinal tract [13,21,23,27,37,38].…”

“…GADs are also present in non-neuronal tissues such as chromaffin cells of the adrenal gland, erythrocytes, endothelial cells of blood vessels, endocrine cells of the gastrointestinal tract and the pancreas, hepatocytes, oocyte of ovary, and epithelial cells of the oviduct [14,22,27,38]. In addition, GAD65 and/or GAD 67 mRNAs have been found in many tissues such as germinal cells and spermatocytes of testis, spleen, liver, mucosal epithelial cells of the oviduct, and pancreatic B cells [18,39].…”