Morphology and physiological significance of parathyroid glands in reptilia

Abstract

Adult reptiles possess one or two pairs of parathyroid glands that have been shown in many species to derive from the third and fourth pharyngeal pouches, respectively. Up to five pairs may develop during early embryonic life. Excess glands may involute during late embryogenesis. The location of the parathyroid glands differs in the various species. As a general rule, they lie just anterior to the heart, the anterior pair (parathyroid III) being associated with the carotid artery, the posterior pair (parathyroid IV) with the aortic arch. In snakes, however, the anterior pair (parathyroid III) is associated with the carotid artery near the angle of the jaw. As shown by light microscopy and, to a lesser extent, by electron microscopy, the parathyroid parenchyma comprises secretory cells which may form dark and light variants, occasional oxyphil cells, and stellate cells. They are arranged in cords separated by connective tissue containing a capillary network. Parathyroid secretory cells often form follicles which might be the result of degeneration. Degeneration may occur as a form of involution during winter in species undergoing seasonal changes. The product of parathyroid cells, the parathyroid hormone, is responsible for the maintenance of blood calcium concentration. The sites of action--bones, kidneys, intestine, endolymphatics, and dermal skeleton--are not well understood or not investigated. In some turtles, parathyroid hormone is not the (main) factor for the regulation of calcium homeostasis.

Ultimobranchial and parathyroid glands of the pigeon Columba livia in response to 1,25(OH)2D3 administration

“…This derives support from the studies on chicks , Sturnus contra (Swarup and Das, 1974) and Psittacula psittacula (Swarup et al, 1986-87) which describe hypercalcemia after administration of either calcium chloride or vitamin D treatment. The present study is also in conformity with the reports of other investigators who have noticed similar effect of vitamin D/its metabolites in various vertebrates-fish (Fenwick et al, 1984;Srivastav, 1983Srivastav, , 1989Singh, 1989, 1992;Srivastav et al, 1993Srivastav et al, , 1997aSrivastav et al, ,b, 1998Srivastav et al, , 2008Sundell et al, 1993;Swarup et al, 1984), amphibia (Srivastav et al, , 1999(Srivastav et al, , 2008, reptile (Srivastav and Rani, 1992;Srivastav et al, 1995Srivastav et al, , 2008Swarup et al, 1987) and mammals (Sawicki et al, 2006;Srivastav and Rani, 1988;Swarup and Srivastav, 1979).…”

“…This is in conformity with the reports of other investigators who describe similar effect of vitamin D or its metabolites in vertebrates (Fenwick et al, 1984;Srivastav and Singh, 1992;Srivastav et al, 1986Srivastav et al, , 1987Srivastav et al, , 1995Swarup et al, 1984). This effect of 1,25(OH) 2 D 3 may be due to the increased intestinal phosphorus uptake and/or mobilization of phosphorus from bone and soft tissues.…”

1,25(OH)2D3 Induced Alterations in Plasma Calcium, Inorganic Phosphate, Ultimobranhial Gland and Parathyroid Gland of the Garden Lizard, Calotes Versicolor

“…In C. versicolor the hyperphosphatemic effect of 1,25(OH) 2 D 3 suggests that non-dietary phosphorus, possibly from the bone or the soft tissues can be mobilized. There exists a single report regarding the effect of 1,25(OH) 2 D 3 on blood phosphate level of a reptile snake (SRIVASTAV et al, 1995).…”

“…Reptiles are in many respects an interesting class of vertebrates as they represent the mainstream of tetrapod evolution (DACKE, 1979;SRIVASTAV et al, 1995SRIVASTAV et al, , 1998a. During water to land transition, probably the most important adaptation was the shelled amniotic egg, which eliminated the need for an aquatic habitat for egg laying, and the hazardous free living larval stage present in many amphibians.…”

“…In reptiles, the parathyroid and ultimobranchial glands have been the subject of extensive research (CLARK 1965,1971a, b, 1983, SEHE 1965, OGURO 1969, 1970, 1972, SENIOR 1974, CLARK and LAVERTY 1985, CLARK et al 1986, YAMADA et al 2001, SRIVASTAV et al 1995, 1998, however, the effects of 1,25(OH) 2 D 3 (biologically active metabolite of vitamin D) on these glands in reptiles have not been investigated. Hence, in this study we have made an attempt to investigate the effects of 1,25(OH) 2 D 3 on the plasma calcium and inorganic phosphate levels as well as on the histological changes in the ultimobranchial and parathyroid glands of the Indian garden lizard, Calotes versicolor.…”