Membrane Ca²⁺ Permeability and Calcium Antagonistic Effects in Resistance Vessels of Spontaneously Hypertensive Rats

Summary

This study compares resting and stimulated ⁴⁵Ca entry in vitro in mesenteric resistance vessels (MRV) of Wistar-Kyoto (WKY) rats and spontaneously hypertensive rats (SHR). The stimulating agent used was norepinephrine (NE). The results show clearly that Ca²⁺ influx into smooth muscle cells from resistance vessels was much higher in the SHR than in the WKY rats. Potential sensitive Ca²⁺ channels (PSC) and receptor-operated Ca²⁺ channels (ROC) may possibly be involved, although there is as yet no evidence for the existence of ROC in MRV in the rat. Further investigations are now needed to establish whether the enhanced stimulated Ca^{2 +} entry is related causally to increased peripheral resistance, i.e., whether it occurs in vivo and what temporal relation it has to the onset of hypertension. Mechanistically, it remains to be established which aspect of channel function is involved in the enhanced Ca^{2 +} entry, and how this is connected with cation stabilization of smooth muscle plasmalemmae in hypertensive individuals.