Blood Flow and Mineral Content of the Tibia of Female and Male Rats: Changes Following Castration and/or Administration of Estradiol or Testosterone

Abstract

We studied changes in the local circulation and mineralization of the rat tibia under different experimental conditions. Four experiments were performed on a total of 155 female and male rats: after oophorectomy (OOX) or orchidectomy (ORX), after the administration of estradiol benzoate (EB, Agofollin Depot, 1 mg/rat once a week or 5 mg/kg body weight once every 5 days for 4 weeks), or after the administration of testosterone (T, Agovirin Depot, 25 mg/kg body weight once every 5 days for 4 weeks). We estimated 85Sr-microsphere uptake and blood flow in the tibia, density of the tibia, and ash weight per bone volume unit. The scheme of the experiments was uniform: experiment A—females—controls, OOX, EB, OOX + EB; experiment B—males—controls, ORX, EB, ORX + EB; experiment C—females—controls, OOX, T, OOX + T; experiment D—males—controls, ORX, T, ORX + T. A sham operation was performed on the animals in the uncastrated groups. The results showed that OOX and ORX stimulated the uptake of 85Sr-microspheres and bone blood flow and reduced both bone density and ash weight, whereas T inconstantly and EB constantly reduced 85Sr-microsphere uptake and bone blood flow and increased bone density and ash weight in both sham-operated and castrated animals. The described changes in the bone blood flow and mineral content under the given experimental conditions suggest a relation in the regulations of both processes, a possible association with resorption of bone, and the importance of the circulation of blood in the metabolism of bone tissue.