Effects of acute intravenous infusion of calcium chloride on the renal concentrating and diluting mechanisms in man

Comparison of intravenous (3-amino-1-hydroxypropylidene)-1, 1-bisphosphonate and volume repletion in tumour-induced hypercalcaemia

In a group of thirty patients with tumour-induced hypercalcaemia the effects of volume repletion and intravenous (3-amino-1-hydroxypropylidene)-1, 1-bisphosphonate (APD) were examined. Volume repletion was only partially effective in lowering serum calcium and raising glomerular filtration rate and it increased the tendency towards hypomagnesaemia. In twenty-nine of the patients serum calcium, serum magnesium, and glomerular filtration rate were rapidly restored to normal by intravenous APD, in doses of 1.75-30 mg/day. Tubular reabsorption of phosphate was lower than normal in five of nine patients in whom it was studied and remained unchanged despite correction of hypovolaemia and serum and urine calcium levels or changes in parathyroid hormone. These findings suggested that tumours may produce a phosphate-lowering factor. The improvement in clinical condition with volume repletion depends on its ability to adjust calcium excretion to the abnormal production of calcium from bone. APD, in contrast, returns pathological bone destruction to normal without any undesirable side-effects.

Renal function in hypercalcemic dogs during hydropenia and during saline infusion

The effects of calcium-gluconate infusions on renal function were studied in unanesthetised dogs. Each dog was studied during hydropenia and saline infusion. Hypercalcemia, mean serum calcium 3.85 mmol/l (hydropenia) and 3.62 mmol/l (saline infusion), increased fractional excretion of sodium (CNa/CIn), calcium (CCa/CIn), and magnesium (CMg/CIn). The increase was significantly higher in saline-expanded dogs than in hydropenic dogs. Fractional excretion of potassium (CK/CIn) was increased in hydropenia but remained unchanged in saline-expanded animals. Fractional excretion of phosphate (Cp/CIn) was not consistently changed by hypercalcemia. Fractional excretion of chloride (CCl/CIn) was markedly increased in saline-expanded dogs but was not changed in hydropenia. Urine osmolality was reduced in hydropenic dogs but unchanged in saline-expanded dogs. In hydropenic as well as in saline-expanded dogs tubular reabsorption of solute-free water (TcH2O/CIn) increased during the first hour of hypercalcemia. In hydropenic dogs hypercalcemia caused a slight but significant decrease in blood pH, standard bicarbonate, and base excess. In hydropenic as well as in saline-expanded dogs glomerular filtration rate (CIn), renal plasma flow (CPAH), and filtration fraction were unaffected.

Effects of hypercalcemia on water and sodium excretion by the isolated dog kidney

The effects of acute hypercalcemia on hemodynamics and on water and sodium excretion were studied on the blood-perfused isolated dog kidney. This model advantageously eliminates various factors which modify medullary osmolality and intrarenal hemodynamics, as well as collecting duct permeability. Calcium ion directly inhibits sodium reabsorption in the proximal tubule and in the ascending limb of Henle's loop, leading to increased sodium excretion rate and to decreased free water generation. The vasoconstrictive action of calcium, leading to decreased glomerular filtration rate, may mitigate the strong natriuretic effect of this ion.