THE DEVELOPMENT OF LASER-FLUOROMETRIC MICROSCOPE FOR MEASUREMENT OF INTRACELLULAR CALCIUM IONS SINGLE LIVING CELLS.

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We have developed an accurate and sensitive system for the measurement of cytoplasmic free calcium concentrations ([Ca^<++>]_i) of a single vascular smooth muscle cell (VSMC) by using UV-laser and Indo-1. [Ca^<++>]_i in spontaneously hypertensive rat (SHR) was elevated and maintained after the 6th passage culture. And moreover, marked elevation of [Ca^<++>]_i after stimulation with caffeine and angiotensin-II occurred in VSMC in some populations of 4-week-old SHR even when blood pressure and basal [Ca^<++>]_i had not yet been elevated. In 8-week-old rats, the basal [Ca^<++>]_i from SHR was elevated compared with Wistar Kyoto rats. We have attempted to characterize yet unspecified circulating factor(s) from SHR serum that elevates [Ca^<++>]_i in VSMC. Our results showed that 1) the maintenance of high [Ca^<++>]_i levels in VSMC in SHR is genetically regulated and it is one of the mechanisms in SHR hypertension, 2) abnormal calcium regulation in VSMC from SHR is expressed even prior to overt hypertension, and 3) the [Ca^<++>]_i elevating factor(s) exists in 8W-SHR serum, but not in 4W-SHR, 4W- or 8W- WKY serum.