Saline ingestion stimulates the in situ molar activity of tyrosine hydroxylase in the median eminence and superior cervical ganglion

The effects of drinking saline for 7 days on the mass and in situ activity of tyrosine hydroxylase (TH) in the median eminence (ME) and superior cervical ganglion (SCG) of rats were investigated. TH mass was quantified by immunoblot assay. In situ TH activity was calculated from the rate of intracellular accumulation of l-dihydroxyphenylalanine (DOPA). In rats that drank 10 mM, 30 mM, and 100 mM NaCl for 7 days, TH activity in the ME was 34 ± 4, 36 ± 5, and 45 ± 3 (mean and S.E.M.) mol of DOPA·h^-1·mol of TH^-1, respectively, compared to 30 ± 2 for rats that drank water. The activity of TH in the SCG of animals that drank 10 mM, 30 mM, and 100 mM NaCl was 143 ± 24, 167 ± 12, and 272 ± 13 mol DOPA·h^-1·mol TH^-1, respectively, compared to 119 ± 10 for animals that drank water. The mass of TH in the ME and SCG decreased as a function of the concentration of NaCl in the drinking water. In animals that drank water, 10 mM, 30 mM, and 100 mM NaCl, the amounts (pmol) of TH were, respectively, 0.28 ± 0.03, 0.31 ± 0.04, 0.23 ± 0.02, and 0.21 ± 0.01 per ME and 0.67 ± 0.06, 0.72 ± 0.11, 0.37 ± 0.01, and 0.34 ± 0.02 per SCG. TH activity in the ME or SCG was unaffected by treatment for 7 days with arginine vasopressin. The mean concentration of dopamine and that of norepinephrine in hypophysial portal plasma of the animals that drank 100 mM NaCl were more than twice that of animals that drank water. It is concluded that the in situ molar activity of TH in the ME and SCG as well as the secretion of dopamine into portal blood are stimulated by ingestion of saline.