Vascular Actions Of Three Chemically Distinct Groups Of Vasoactive Hormones

The whole body, tissue and cellular effects of three chemically distinct groups of vasoactive hormones are compared. These hormones include peptides (AVP and PTH), steroids, estrogen, 1,25(0H)₂D₃ and 24,25(0H)₂D₃, and the newly discovered parathyroid hypertensive factor (PHF) which has a proposed structure of a lysophosphatidyl peptide. The peptides produce acute changes in blood pressure. The steroids do not have any overt effect on blood pressure. PHF has an unique delayed hypertensive effect. It is suggested that peptides may be important in short term immediate blood pressure regulation, while PHF and steroids are more involved in medium and long term modulation of vascular sensitivity to other vasoactive substances.Some interesting features have been demonstrated for each vasoactive hormone studied. AVP exclusively utilizes the extracellular source of Ca²⁺ for its vasoconstricting activity in rat tail artery, unlike the aorta, which has been reported to depend on intracellular stored Ca²⁺. However, AVP can also release intracellular stored Ca²⁺, but not vascular contraction in rat tail artery. Furthermore, AVP inhibits vascular contractions dependent on intracellular stored Ca²⁺ release produced by NE. PTH can elicit an initial increase in [Ca²⁺], and subsequent inhibition of stimulated [Ca²⁺], increase in...