Rapid effects of parathyroid hormone(1-34) and prostaglandin E2 on bone blood flow and strontium clearance in the rat in vivo

Abstract

The vascular effects of noradrenaline, ATP, parathyroid hormone (PTH) and prostaglandin E2 (PGE2) were investigated in the rat. Additionally, the exchange of mineral ions between bone and blood was assessed by measuring strontium clearance, with the aim of investigating whether the vascular effects of these agents altered uptake of mineral ions or if this exchange could be changed independently of blood flow. Radioactive microspheres and 85Sr were used to establish bone blood flow and mineral clearance. Measurements of bone blood flow and arterial pressure were made in each animal and used to calculate vascular resistance. A measurement of 85Sr clearance was also obtained. Arterial blood pressure was significantly affected by noradrenaline (P less than or equal to 0.003) and ATP (P less than or equal to 0.015). Additionally, noradrenaline significantly (P less than or equal to 0.03) reduced bone blood flow. This decrease was related to a significant increase in vascular resistance. Arterial blood pressure and bone blood flow were significantly reduced by both bovine PTH(1-34) (P less than or equal to 0.001, P less than or equal to 0.02) and PGE2 (P less than or equal to 0.005, P less than or equal to 0.001). Vascular resistance to bone was increased by both agents but this was only statistically significant in the case of PGE2 (P less than or equal to 0.01). A significant (P less than or equal to 0.001) reduction in strontium was also produced by PGE2. In each group the relationship between bone blood flow and strontium clearance was then analysed.(ABSTRACT TRUNCATED AT 250 WORDS)