Parathyroid Hormone Responses to Catecholamines and to Changes of Extracellular Calcium in Cows

Abstract

A B S T R A C T Modifications ofthe plasma level of im

Effects of Epinephrine Treatment on the Rat Parathyroid Gland, with Special Reference to the Frequency of Storage Granules

“…Furthermore, the more rapid decrease in NSG after injection of epinephrine in EDTA-induced hypocalcemic rats observed in the present work, well agrees with the data that parathyroid hormone secretion by epinephrine stimulation is more increased under low calcium levels than under normal calcium levels [Blum et al, 1978;Mayer et al. 1979] Recently, ultrastructural changes indicating activa tion of parathyroid parenchymal cells have been reported in vagotomized [Isono ami Shoumura, 1980] and vagus-stimulated rabbits [Isono et al, 1982], In the present observation, however, chief cells of the rats tre ated only with epinephrine showed no distinct alteration in fine structure as compared with those of control ani mals.…”

“…1973;Brown et al, 1977a], In most of these studies, such as action of |3-adrenergic agents has been supposed to be probably mediated by an increase in cyclic AMP in parenchymal cells. Furthermore, this view is supported by some evi dence that (3-adrenergic receptors exist on the parathy roid cell membrane [Brown et al, 1977b] and that (3-adrenergic agonists stimulate production of cyclic AMP [Brown et al, 1977a], In addition, most of the phy siological or biochemical studies on short-term adminis tration of epinephrine have shown that the level of PTI1 first increases rapidly and then returns slowly to a basal level [Fisher et al, 1973;Kukreja et al, 1975Kukreja et al, , 1976Blum et al, 1978;Mayer et al, 1979].…”

“…1975Kukreja et al. , 1976Blum et al, 1978;Mayer et al, 1979] as well as in vitro [Williams et al. 1973;Brown et al, 1977a], In most of these studies, such as action of |3-adrenergic agents has been supposed to be probably mediated by an increase in cyclic AMP in parenchymal cells.…”

Changes in Parathyroid Hormone and Calcium Levels after Superior Cervical Ganglionectomy of Rats

“…The intracellular phenomena implicated in adrenergic regulation of parathyroid cell response to low Ca deserve further exploration. In vivo and in vitro data indicate that PTH response to catecholamines is transient and elapses for only 30-60 min [4,21,22]; indeed catecholamines re lease exclusively old or preexisting PTH while low Ca rec ruits secreted PTH equally from newly synthesized and that stored in secretory granules [17,26]. Once the storage pool is exhausted by NE, PTH declines despite continued activity of adenylate cyclase.…”

“…Agents that increase par athyroid cell cyclic AMP synthesis (e.g. P-adrenoceptor agonists, dopamine) enhance secretion of PTH in vitro [8,10,21,38] and in vivo [4,6,19,24] whereas those substances that lower cyclic AMP (e.g. a-adrenoceptor agonists) inhi bit secretion [5,9,39].…”