The distribution of norepinephrine (NE) and epinephrine (E) between the capsulelglomerular zone and the remainder of the adrenal was studied in the adult female rat. Both catecholamines were present in these two parts of the gland. The concentration of E was higher than that of NE. In the capsule/glomerular zone the catecholamine concentrations were more than twenty to thirty times lower than in the inner part of the gland. The circulating levels of catecholamines were always very low. The present data also support very weak or no changes in catecholamine concentrations in both parts of the adrenal during the different stages of the estrous cycle.The plasma levels of both aldosterone and corticosterone, like those of catecholamines, did not vary significantly throughout the estrous cycle. One week after unilateral or bilateral demedullation, both E content and concentration were reduced in the whole capsule/glomerular zone of the adrenal although the NE content did not change. The reduction of NE concentration could be related to the drastic weight increase of this part of the gland on the operated side. Moreover, unilateral dernedullation was unable to significantly modify the plasma levels of both E and NE. In contrast bilateral demedullation suppressed circulating E and induced a significant reduction (about 50%) of NE plasma level. The present data suggest: 1) an extra-adrenal origin for the NE innervation of the capsule/glomerular zone of the adrenal cortex, and 2) a dual origin for E in the capsulelglomerular zone; part of E could arise from the adrenal medulla and part from an extra-adrenal site.The existence of functional interactions betwecn the adrenal cortex and the medulla is well supported. Indeed, Wurtman and Axelrod ( I ) in thc adult rat and Margolis r t ril. (2) in the fetal rat showed that the development of the phcnylethanolaminc-Nmethyl transferase (PNMT) activity, which allows epinephrine (E) synthesis from norepincphrine (NE), is controlled by glucocorticosteroids. Further experiments determined the role of adrenocortical hormoncs in the modulation of synthesis and dcgradation of the enzymes involved in the formation of catecholamines (CA) (reviews in 3 and 4). Reciprocally E and N E may stimulate aldosterone release (5). but not dopamine (DA), that would act directly at the zona glomerulosa to inhibit aldosterone secretion (6). The zona glomerulosa of the rat adrenal cortex receivcs catecholaminergic innervation (7) but the histofluoresccnt technique uscd cannot specify which biogenic amine is present. However, as immunoreactivity to PNMT was not observed in the adrenal cortex (8) it was unlikely that the histofluorescent fibres contained endogenous E. Recently, Buu and Lussier (9) showed indirectly that tyrosine hydroxylase (TH) activity is also absent from the adrenal cortex although Oomori of ul. (10) pointed out the presence of TH immunoreactive nerve fibres in the separated capsule of the rat adrenal gland. NE could be a neurotransmitter in the zona glornerulosa as suggested b...
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