Prostaglandin E2 binding and cyclic AMP production in isolated bone cells

Abstract

The binding of prostaglandin E2 (PGE2) to bone cells was studied to provide direct evidence for the existence of specific receptors in bone. Bone cells were isolated by collagenase digestion of fetal and newborn rat calvaria. Isolated cells were incubated with 3H-PGE2 and collected on Millipore filters. Specific binding was determined by subtracting the binding that occurred with 10(-6) M non-radioactive PGE2 and 3H-PGE2 from that with 3H-PGE2 alone. With heterogeneous cell preparations and at PGE2 concentrations from 10(-9) - 1.7 X 10(-8) M at 37 degrees C, specific binding reached steady state within 10 min. Bound 3H-PGE2 was displaced by the addition of increasing amounts of unlabeled PGE2. Inhibition of PGE2 binding was observed with PGE1 and the endoperoxide analog, U44069, but not with PGF2 alpha, a lipopolysaccharide, or 13,14-dihydro 15-keto PGE2. Studies with bone cell populations, obtained by sequential digestions, indicated that an osteoclastic population binds 30-fold more PGE2 than osteoblastic cells. Scatchard analyses revealed that the osteoclastic cells have an affinity constant for PGE2 binding similar to that obtained with heterogeneous populations. However, the PGE2 binding capacity in this osteoclastic population was fivefold greater than in the heterogeneous population. The osteoclastic population responded with an increase in cyclic AMP to lower concentrations of PGE2 than the osteoblastic populations. These studies suggest that differences in the binding capacity of PGE2 receptors exist among bone cell-types and that these differences are reflected in the cellular cyclic AMP response.

Inhibition of cyclooxygenase by indomethacin modulates osteoblast response to titanium surface roughness in a time‐dependent manner

“…12, 2001 / 52-61 Prostaglandins are important mediators of osteoblastic differentiation (Dziak et al 1983;Nemoto et al 1997;Sabbieti et al 1999). Local regulation of bone formation occurs in a physiological background regulated by the endocrine system, including hormones such as 1,25-(OH) 2 D 3.…”

Adriamycin inhibits PTH-mediated but not PGE2-mediated stimulation of cyclic AMP formation in isolated bone cells

“…Indeed, the cell cultures used in the present study do not contain a homogeneous population, but osteoblastlike cells are in the majority, as indicated by a variety of biochemical criteria. Osteoblasts possess receptors for prostaglandins of the E series, and respond to prostaglandins with increases in cyclic AMP formation [4][5][6]. It is reasonable to suggest, therefore, that the cyclic AMP response in our experimental system stems mainly from osteoblasts (or osteoblastlike cells).…”

“…Rises in cellular cyclic AMP and Ca 2 § levels trigger a cascade of metabolic events that culminates in purposive cell behavior. There is reason to believe that prostaglandins of the "E" series (PGE) act in similar fashion to influence osteoblast function [4,5]; PGE binds specifically to osteoblastlike cells and stimulates cyclic AMP formation [6].…”

Osteoblastic differentiating potential of dental pulp stem cells <i>in vitro</i> cultured on a chemically modified microrough titanium surface

“…Even though high levels of prostaglandins are associated with inflammation, prostaglandins are important mediators of osteoblastic differentiation. PGE2 is needed for the increase of TGF-β1 and both molecules are needed in later stages for DPSCs terminal differentiation by increasing alkaline phosphatase specific activity [41][42][43] . In the present model an increase of PGE2 secretion level released by cells grown on test compared to those exposed to control surfaces was recorded, thus confirming the hypothesis of a more prominent osteoblastic differentiation on test surfaces.…”