The Relaxant Effects of Parathyroid Hormone(1‐34) and Parathyroid Hormone‐Related Protein(1‐34) on Ovine Reticulo‐Ruminal Smooth Muscle in Vivo

Abstract

summaryThe motility of the reticulo-rumen has been measured in trained, conscious sheep using inflated balloons temporarily introduced to selected regions of that forestomach. The frequency and amplitude of the contractions of the reticulum and both the A and B waves of contraction of the rumen were measured under the same conditions before, during and after the administration of an i.v. bolus of either parathyroid hormone (PTH(1-34)) or PTH-related protein (PTHrP(1-34)) followed by its i.v. infusion. These two peptides are known to share a common receptor in other organs, e.g. the kidney. In this study they both showed an inhibitory effect on reticulo-ruminal motility. The effect of PTHrP(1-34) on the rate of ruminal blood flow was also examined and a significant reduction observed, after a transient increase. The secretion of endogenous PTH(1-34) was stimulated by a 32% reduction in the plasma calcium ion concentration induced by an i.v. infusion of sodium citrate. Associated with this were significant reductions in reticulo-ruminal motility, e.g. the reduction in the mean amplitude of the reticular contractions reflected the reduction in plasma calcium ion concentration. ]PTHrP(7-34) before and during the induction of hypocalcaemia, all but one of the parameters of reticulo-ruminal motility were normalized. Indeed, by the day following the administration of this blocking agent, all these parameters had returned to their normal range. It is concluded that stimulation of the PTH(1-34)ÏPTHrP(1-34) receptor in reticulo-ruminal smooth muscle reduces the motility of this tissue and may play a role in the depression of motility of the digestive tract which is characteristic of clinical milk fever in the dairy cow. introduction Although ruminants largely depend upon the enteric nervous system for the reflex control of mixing contractions in the reticulo-rumen, endocrine influences are also involved. One of these is shown here to be parathyroid hormone-related protein (PTHrP (1-34)) which has been demonstrated to share a receptor on both osteoblasts and renal distal tubules with PTH(1-34) (Nissenson et al. 1988) and also on rat fundic strips (Mok et al. 1989). Another is gastrin which acts both centrally and peripherally to reduce the motility of the reticulum (Grovum, 1986).Although not yet studied in sheep, the expression o PTHrP in the stomach of the rat has been shown to be induced by mechanical stretch (Cooper et al. 1991) and also by contractions induced by carbachol (Ito et al. 1994). Moreover, from in vitro experiments using fundic strips of rat stomach, it has been shown that the addition of PTHrP(1-34) significantly reduces

Effects of feeding synthetic zeolite A during the prepartum period on serum mineral concentration, oxidant status, and performance of multiparous Holstein cows

“…Therefore, a greater proportion of the EXP diet had a smaller particle size due to the zeolite A compared with the CON diet. In sheep, PTH has been shown to have relaxing effects on the reticulo-rumen smooth muscle, resulting in decreased ruminal contractions (Care et al, 1999). Although we did not measure blood PTH concentrations in the current study, it is plausible that the EXP-fed cows had increased circulating PTH compared with the CON-fed cows, resulting in slight differences in rumination rates.…”

Diagnostic and prognostic significance of serum gastrin and pepsinogen in dairy cows with displaced abomasum

“…These diseases included ketosis, retained placenta, milk fever, mastitis and metritis. Other studies also reported an association of ketosis, hypocalcaemia and milk fever with DA (Massey et al, 1993;Oikawa et al, 1997;Care et al, 1999). Duffield & Bagg (2002) also added that herds with ketosis in early lactation cows were at risk of increased incidence of DA (>8%) and increased herd removals in the first 60 DIM (<8%).…”

Transient severe hypotension with once-weekly subcutaneous injection of teriparatide in osteoporotic patient: a case report and insight for the drug interaction between hypotensive agents and teriparatide

“…This is the first report describing such a severe transient hypotension after once-weekly injection of teriparatide. The mechanism of hypotension after injection of teriparatide was generally believed due to the vasodilating action through the vascular smooth muscle relaxant activity, accompanied by pulse increase (11,12). Hypotension has multiple possible causes, and hypotensive agents such as Ca 2 antagonist reduce vascular smooth muscle tone with increase of vessel diameter and decrease of the blood pressure (13).…”