Regulation of plasma calcium in rats: age-related roles of PTH and calcitonin

Abstract

To determine the influence of aging on the relative roles of parathyroid hormone (PTH) and calcitonin in the control of calcium homeostasis during fasting, we assessed changes in plasma calcium in fasted rats following simultaneous removal of the glands that secrete both hormones. Animals ranging in age from 3 to 34.7 wk were thyroparathyroidectomized or sham operated and bled by orbital puncture prior to and 1.5, 3, and 6 h after surgery. After thyroparathyroidectomy (TPTX), plasma calcium fell immediately and progressively in very young rats (3-6 wk old); in young animals (6.5-9.4 wk old), there was a delay of about 1.5 h pceded by a rise, which persisted for at least 3 h. Since the rise and fall in plasma calcium after TPTX are most likely due to calcitonin and PTH deficiencies, respectively, our observations are consistent with the following hypothesis; in the fasting state, the relative importance of calcitonin and PTH in the regulation of plasma calcium varies with age; PTH appears to play the dominant role in young rats; however, during maturation the importance of calcitonin appears to increase progressively.

Effects of Starvation on the Ultrastructure of the Mouse Parathyroid Gland

“…The serum calcium concen trations of the starved rats are significantly lower than those of the controls, and the starved rats lose approxi mately 25-30% of their initial body weight [Shires et al, 1980]. In addition, it has been demonstrated that in the fasting state the relative importance of calcitonin and parathyroid hormone in regulation of serum calcium varies with age, and parathyroid hormone plays a do minant role in young rats [Kalu and Foster, 1976]. We have pointed out that the serum calcium concentrations of the starved mice are not changed and the body weights of the test animals show a significant decrease as compared to those of the control animals.…”

Upregulation of HB‐EGF, Msx.1, and miRNA Let‐7a by administration of calcitonin through mTOR and ERK1/2 pathways during a window of implantation in mice

“…It is widely accepted that calcitonin increases intracellular calcium (Ca 2+ ) levels and calcium acts as an important secondary messenger and plays a role in a series of cellular functions such as cell proliferation, cell differentiation, and fetal development (Li, Shen, Chang, Hsu, & Sung, 2008). Also, it has been reported that increased intracellular calcium concentration can lead to increased blastocyst formation and implantation (Kalu & Foster, 1976). It was found that after fertilization, the uterine endometrium begins to express calcitonin, and the calcitonin expression reaches the highest level during the implantation window (Ding, Zhu, Bagchi, & Bagchi, 1994;Kumar et al, 1998;Zhu, Cullinan-Bove, Polihronis, Bagchi, & Bagchi, 1998).…”

Effects of Starvation on the Water-Clear Cell in the Golden Hamster Parathyroid Gland

“…It has become apparent as a result of physiological studies that starvation had an effect on calcium metabolism (Kalu and Foster, 1976 Asch and Asch, 1981). Recent morphological reports have suggested that in the chief cells of the parathyroid glands in the starved mice (Isono et al, 1985) and golden hamsters ) the number of lipid droplets were increased as compared to those of the control animals.…”

“…Physiological studies have shown that starvation had an effect on calcium metabolism (Kalu and Foster, 1976;Asch, 1978;Beck et al, 1979;Pak and Galosy, 1979;Shires et al, 1980;Asch and Asch, 1981). Recent morphological reports have suggested the changes of the parathyroid glands in starved mice (Isono et al , 1985) and starved golden hamsters .…”