WATER-DEPRIVATION AND RAT ADRENAL MESSENGER-RNAS FOR TYROSINE-HYDROXYLASE AND THE NOREPINEPHRINE TRANSPORTER

Experiments were performed in rats to test the hypothesis that adrenal mRNA levels of tyrosine hydroxylase (TH) and the norepinephrine trans porter (NET) would be modified by water deprivation via activation of the sympathetic nervous system. TH and NET mRNA levels were measured u sing the ribonuclease protection assay. Adrenal TH mRNA was higher (P < 0.001) in water-deprived (921 +/- 39 fg/mu g total RNA) compared wit h the water-replete rats (657 +/- 45 fg/mu g total RNA). In contrast, water deprivation decreased (P < 0.01) adrenal NET mRNA levels (275 +/ - 66 vs. 433 +/- 63 fg/mu g total RNA). The dehydration-induced increa se in TH mRNA was prevented by prior splanchnicectomy, but the decreas e in NET mRNA was produced even in the absence of adrenal nerves. Wate r deprivation also increased (P < 0.05) plasma adrenocorticotropic hor mone (84 +/- 16 vs. 42 +/- 14 pg/ml) and corticosterone (358 +/- 87 vs . 44 +/- 15 ng/ml) levels. Interestingly, the corticosterone response was reduced (P < 0.05) by unilateral adrenal denervation. These result s suggest that water deprivation increases both adrenal medullary and adrenocortical activity at least in part by stimulation of sympathetic nerve activity.