Subject(s)
Alkaline Phosphatase/blood , Bone and Bones/enzymology , Isoenzymes/blood , Wheat Germ Agglutinins , Adult , Child , Child, Preschool , Female , Hepatitis/enzymology , Humans , Infant , Male , Osteitis Deformans/enzymologyABSTRACT
The administration of 1,25-dihydroxycholecalciferol to rats increased their calciuresis as a power function of the dose. Up to 95% of the urinary calcium was excreted as a non-ionized complex, together with equimolar amounts of citrate. The stoichiometry between calcium and citrate, observed at all dose levels, suggests that citrate metabolism is coordinated with the mobilization of calcium.
Subject(s)
Calcitriol/pharmacology , Calcium/urine , Animals , Citrates/blood , Citric Acid , Creatinine/urine , Diuresis/drug effects , Kidney/analysis , Kidney/drug effects , Male , Rats , Rats, Inbred StrainsABSTRACT
The daily administration of supraphysiological doses of 1,25 dihydroxycholecalciferol (0.1-2.5 micrograms/d/100 g body weight) to rats, produced respiratory alkalosis. With the doses of 0.1-0.2 micrograms/d/100 g and feeding a diet with 0.7% of calcium, calcemias did not exceed 2.75 mM, and significantly reduced plasma ionized calcium levels were measured. The latter phenomenon was found associated with increased urinary excretion of cAMP, soft tissue calcium content, and polyuria with hypostenuria, all known effects of parathyroid hormone. These effects were absent in thyroparathyroidectomized rats treated in the same fashion. Present results suggest that the stimulus of low levels of plasma ionized calcium overcomes the probably inhibitory effect of the steroid on parathyroid hormone secretion.
Subject(s)
Alkalosis, Respiratory/chemically induced , Calcitriol/pharmacology , Calcium/blood , Animals , Calcium/metabolism , Cyclic AMP/urine , Dose-Response Relationship, Drug , Kidney/metabolism , Parathyroid Glands/physiology , Polyuria/chemically induced , Rats , Rats, Inbred Strains , ThyroidectomyABSTRACT
The Ca metabolism of pancreatectomized (PX) rats was investigated three months after surgery. Most PX animals were in negative Ca balance because of increased endogenous fecal Ca excretion and reduced true Ca absorption. Significant increases were also observed in bone Ca resorption rates, hydroxyproline excretion and size of osteocyte lacunae. Inverse correlations between the rates of bone Ca resorption and Ca balance were observed in the PX and control groups. Significantly, both correlations were found to fit the same function. It was concluded that parathyroid hormone secretion and its metabolic expression were not impaired by pancreatectomy. The coupling between bone Ca accretion and resorption was absent in PX animals: high resorption rates were found associated with normal or decreased accretion rates. These latter rates, in combination with the negative Ca balance, explain the reduction in the skeletal Ca mass.
