Abstract
The endogenous catecholamine content, norepinephrine retention, and the activity of enzymes involved in the synthesis and degradation of catecholamines were examined in several organs of inbred rats which developed hypertension as a result of triiodothyronine and NaCl administration. In hypertensive inbred rats given triiodothyronine and NaCl there was a decrease in content and retention of H3-nor-epinephrine. The decreased retention of H3-nor-epinephrine in hypertensive rats reflects increased turnover of the amine. Normotensive inbred rats not given triiodothyronine and NaCl had an increased norepinephrine content in the heart when compared to non-inbred control rats. Cardiac monoamine oxidase activity was increased, but catechol-O-methyl transferase unaltered in the hypertensive rats. The norepinephrine content in the gut and submaxillary gland was increased as a result of inbreeding, but the development of hypertension decreased the content to the range of noninbred control tissues. An increased retention of H3-norepinephrine was found in the gut and submaxillary gland as a result of inbreeding alone, and this was not altered by the presence of hypertension. Adrenal tyrosine hydroxylase activity, phenylethanolamine-N-methyl transferase activity and epinephrine were slightly elevated in the inbred hypertensive group, but no change in sympathetic ganglia tyrosine hydroxylase activity was demonstrated. Thus it appears that the hypertensive state produced by triiodothyronine and NaCl is accompanied by changes in catecholamine storage and synthetic enzymes whick in general resemble those previously reported for DOCA-NaCl hypertensive rats.