Immunoreactive beta-endorphin levels in plasma and pituitary tissue from genetically hypertensive and normotensive rats. 
1.  Levels of immunoreactive beta-endorphin were measured in neurointermediate lobes, anterior lobes and plasma from the Japanese and New Zealand strains of genetically hypertensive rats and their normotensive controls.  2.  No significant differences were observed in beta-endorphin between the hypertensive and normotensive rats of the New Zealand strain.  3.  The hypertensive rats of the Japanese strain showed significantly higher levels of beta-endorphin in neurointermediate lobe and lower levels in plasma than their normotensive controls.  4.  These results suggest that the differences in beta-endorphin levels in the Japanese strain reflect a genetic difference not necessarily related to elevated blood pressure.