Role of calcitonin in the rapid minute‐to‐minute regulation of plasma Ca²⁺ homeostasis in the rat

Abstract

Acute removal of the tonus of CT results in an acute increase in plasma Ca2+ for up to 3 h. This effect of CT is probably mainly related to the postprandial maintenance of normocalcaemia, but is also seen in fasting rats, although to a lesser degree. The very rapid calcaemic recovery after discontinuation of a brief induction of hypocalcaemia is, however, not a result of suppressed plasma calcitonin levels.

Blood Calcium Levels in Immature Rats: Influence of Extracellular Calcium Concentration on Myocardial Calcium Handling

“…The neonatal values determined in this study were comparable to those measured not only in adult rats from different strains (1.2-1.4 mmol/l [16,26,28]; present results), but also in healthy, full-term human newborns and in adult humans (reference interval: 1.1-1.4 mmol/l [1, 18, 21]). …”

Rate‐dependency of calcitonin secretion in response to increased plasma Ca2+

“…Although a considerable amount of extra‐thyroidal CT production takes place in many different tissues (e.g. small intestine, thymus, liver and lung) and contributes to the serum concentration of CT in monkeys and humans [15], the plasma CT levels in the present study declined to levels undetectable with the assay used shortly after acute TPTX and TX in rats [16], indicating that in rats the C‐cells of the thyroids are the main source of circulating CT. The existence, however, of a minimal response by the CT secretion to hypocalcaemia seemed to suggest that the CT secretion could not be totally suppressed, even at very low concentrations of calcium.…”

Key role of the kidney in the regulation of fibroblast growth factor 23

“…83 Our laboratory has previously demonstrated a rapid minute-to-minute regulation of p-Ca 2+ , where the set point for Ca 2+ on the bone surface was defined by the level of calciotropic hormones, activity of CaR, and the presence of kidneys. [84][85][86][87][88] The minute-to-minute regulation of P is not well understood. A rise in p-P resulted not only in an immediate dose-dependent drop in p-Ca 2+ but also in prolonged recovery in BNX rats.…”