Levels of dopamine and 3,4-dihydroxyphenylacetic acid in the adenohypophysis of normo- and hypertensive rats.

The levels of dopamine and its metabolites in the adenohypophysis of the normo- and hypertensive rats were determined. Dopamine was present as the free and sulfate-conjugated form in the adenohypophysis of the spontaneously hypertensive rat (SHR), Wistar Kyoto (WKY) and Sprague-Dawley (SD) rats. The levels of both the free and conjugated dopamine in the adenohypophysis of the SHR were 5.49 +/- 2.91 (mean +/- SEM) and 4.27 +/- 3.31 pmoles/mg protein respectively. These values were not significantly different from those of the WKY and SD. 3,4-Dihydroxyphenylacetic acid (dopac), present as the free and sulfate-conjugated form, was found to be the only metabolite of dopamine in the adenohypophysis of the three animals. The levels of both free and conjugated dopac in the adenohypophysis of the SHR were 7.0 +/- 2.5 and 75.5 +/- 33.5 pmoles/mg protein respectively and these values were significantly different from those of the WKY (1.12 +/- 0.47 and 4.17 +/- 0.48 pmoles/mg protein) and SD (1.87 +/- 0.62 and 3.5 +/- 1.11 pmoles/mg). The results indicate that (a) there is no deficiency of free dopamine in the adenohypophysis of the SHR and hypertension in these animals is unlikely to be related to the catecholamine level in the endocrine gland, (b) the dopamine turnover in either the tuberoinfundibular tract or the adenohypophysis of the SHR is greatly enhanced.