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

Abstract

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 ≤ 0·003) and ATP (P ≤ 0·015). Additionally, noradrenaline significantly (P ≤ 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 ≤ 0·001, P ≤ 0·02) and PGE2 (P ≤ 0·005, P ≤ 0·001). Vascular resistance to bone was increased by both agents but this was only statistically significant in the case of PGE2 (P ≤ 0·01). A significant (P ≤ 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. Only the PGE2-treated group had a slope of the regression which was statistically different from both the control animals and the other drug-treated groups. Treatment with PGE2 therefore resulted in a dose-related decrease in 85Sr clearance which was not related to the reduction in bone blood flow. Journal of Endocrinology (1991) 131, 359–365