Development of the cyclic AMP response to parathyroid hormone and prostaglandin E2 in the embryonic chick limb

Abstract

The developing chick limb was studied to determine the ability of parathyroid hormone (PTH) and prostaglandin E2 (PGE2) to increase intracellular cyclic AMP (cAMP) during various stages of development. All developmental stages examined (stages 20-21, 24-25, and 26-28) responded to PGE2 when the cells were assayed immediately following the removal of the limbs from the embryos. In contrast, only stage 26-28 limb cells responded to PTH when assayed in a similar manner. The response to PTH was temporally correlated with the appearance of cartilage matrix in vivo. Undifferentiated limb cells were also cultured and assayed at various times for hormone responsiveness. Stage 24-25 high-density cell cultures responded initially to PGE2 but not to PTH. However, by 36 h and in all subsequent time intervals tested, the response to PTH was significantly greater than that to PGE2. The PTH receptor, in contrast to that of PGE2, was shown to be sensitive to trypsin treatment, but could be generated during subsequent cell culture. The majority of the hormone-responsive cells were found in cartilaginous regions of the limb, and were shown to respond to both hormones in a dose-dependent manner. The PTH-induced cAMP response was affected by low cell density and mouse serum, both of which significantly inhibit the chondrogenic potential of cultured limb cells. These findings are consistent with a temporal correlation between the development of the PTH response and chondrogenesis in vivo.

Parathyroid hormone stimulates growth of embryonic chick pelvic cartilagein vitro

“…This tachyphylaxis to PTH is similar to the PTH refractiveness in cyclic AMP production in rat calvaria reported by Heersche and Aurbach [25]. There are receptors for PTH in early primordial cartilaginous rudiments and the PTH-adenylate cyclase system is functional [28,29]. This observation suggests that cyclic AMP may trigger growth directly by acting on gene transcription [7].…”

Arachidonate metabolism during chondrogenesisin vitro

“…Interestingly, prostaglandin E 2 alters levels of cyclic AMP in chondrogenic cells [39], and potentiates the stimulation of chondrogenesis by theophyllinc [40]. Fluctuations in levcls of cyclic AMP have been related causally to chondrogenesis [39, 41-441. …”

Influence of prostaglandins on DNA and matrix synthesis in growth plate chondrocytes

“…397 398 OKEEFE ET Al,.levels of prostaglandin E, precedes chondrogenesis, and PGE, has been further demonstrated to directly stimulate the chondrogenesis of undifferentiated limb mesodermal cells through a CAMP-mediated mechanism. (5)(6)(7)(8) Prior work demonstrated prostaglandin synthetase activity in homogenates of growth plate cartilage,'') and recently, prostaglandins of the E series were identified in normal growth plate cartilage in nanomolar concentrations. ( l o ) Prostaglandin E, was found to increase cartilaginous tissue mass in a fracture healing and prostaglandins El, E,, and D, were shown to stimulate the accumulation of cAMP in monolayer cultures of chondrocytes isolated from rabbit ribs.…”