Autoradiographic distribution of radioactivity from14C-GABA in the mouse

Abstract

We investigated the distribution of radioactivity from 14C‐labeled γ‐aminobutyric acid (GABA) in the mouse by in vivo autoradiography to clarify the tissues that show GABA uptake and/or GABA binding. Male mice were injected intravenously with 14C‐GABA in both the absence and presence of an excess of unlabeled GABA, baclofen and isoguvacine. Whole‐body autoradiography of 3H‐baclofen, a GABAB receptor agonist was also performed. At short intervals after 14C‐GABA injection ( 3 and 6 minutes), very high radioactivity was detected in the kidney cortex, liver, pineal gland, hypophysis, median eminence of the hypothalamus, and cervical ganglion. The hyaline cartilage and glandular part of the stomach showed moderate radioactivity. In the presence of an excess amount of unlabeled GABA, radioactivity in most of tissues decreased significantly, but no significant difference in radioactivity was observed in the presence of baclofen and isoguvacine, agonists of GABAA and GABAB receptors, respectively. Autoradiography of 3H‐baclofen showed that the kidney had high level of radioactivity, whereas the activity in other tissues and organs was similar or lower than in the blood except for the content of the urinary bladder and the pancreas at 15 minutes after injection. These data indicate that radioactivity from incorporated 14C‐GABA into a variety of cells is much higher than that from bound 14C‐GABA to the receptor sites. Our results suggest that GABA can be quickly localized in many organs of the mouse body after 3 minutes following injection, and GABA may serve multiple functions in those organs. Microsc. Res. Tech. 41:116–126, 2000. © 2000 Wiley‐Liss, Inc.

The influence of a tomato food matrix on the bioavailability and plasma kinetics of oral gamma-aminobutyric acid (GABA) and its precursor glutamate in healthy men

“…Studies in mice suggest that intravenously administered GABA is distributed extremely rapidly (within 3 minutes after injection), mainly to the liver and kidney, and metabolized to other components, like succinate. [26][27][28] In the liver, GABA-transaminase activity is high and it…”

“…Studies in mice suggest that intravenously administered GABA is distributed extremely rapidly (within 3 minutes after injection), mainly to the liver and kidneys, and metabolized to other components, like succinate. [25][26][27] In the liver, GABA-transaminase activity is high and it is therefore mainly responsible for the catabolism of GABA. 28 The high uptake of GABA from the portal vein into the liver would keep the plasma GABA concentration in systemic circulation relatively low.…”

Anterior pituitary cells excited by GABA

“…Is the source of GABA the portal vasculature capturing GABA released from neurons in the median eminence? It is known that radioactive GABA readily accumulates in the pituitary (Kuroda et al 2000; Duvilanski et al 2000). Is it possible that GABA is released from anterior pituitary cells and thus can be considered an autocrine regulator?…”

Increased GABA Transport Activity in Rat Calvarial Osteoblasts Cultured under Hyperglycemic Conditions

“…10) In addition to these peripheral tissues, the expression of GABA and particular GABAergic signaling molecules is found in bone cells such as osteoblasts 8,9) and chondrocytes. [14][15][16] Amongst different isoforms of GABA transporters required for signal termination, expression of betaine/GABA transporter-1 (BGT-1) is exclusively detected at mRNA and protein levels with a temperature-, sodium-and chloride-dependent activity of [ 3 H]GABA accumulation in osteoblasts, as well as GABAB receptor. 8,9) Although GABAB receptor is shown to play an inhibitory role in osteoblastic differentiation and/or maturation, the role of BGT-1 isoform has not yet been well understood.…”