Detailed mapping of prostaglandin E2 binding sites in the brain

Aside from the great theoretic interest, the experiments described in this paper have considerable practical importance in providing a means of studying the efficacy of treatments designed to prevent kernicterus. A comprehensive study of a strain of rats (the Gunn strain) which have a hereditary deficiency of the enzyme required to conjugate bilirubin, and thus develope jaundice due to increased concentration of unconjugated bilirubin in the blood and tissues. The rats developed kernicterus which was apparently identical with that seen in human beings and is the only example of kernicterus in animals that fulfills rigid criteria outlined by the authors. Extensive data on the natural history of the bilirubinemia and development of kernicterus in the rats, as determined by chemical and pathologic techniques, are provided. Bilirubin itself is incriminated as the toxic agent producing the characteristic changes in the brain in kernicterus. Sulfonamides were found to augment the toxic effects of bilirubin, apparently because of competition between bilirubin and sulfonamides for binding sites on serum albumin. Neither infection nor hypoxia appeared to aggravate the effects of bilirubin. Administration of sodium glucuronate to jaundiced rats was followed by a decrease in bilirubin in the serum which at times exceeded 50%. This was not accompanied by any postponement of the onset of signs of damage to the central nervous system and did not prevent development of kernicterus. It appeared that the decrease in bilirubin in the serum may have resulted from an increased transferral to tissues rather than elimination through renal excretion. On the basis of the knowledge of this strain of rats, it should be possible to explore the usefulness of proposed therapeutic regimens in the experimental animal without jeopardizing the course of human infants who might be successfully treated with exchange transfusion pending the discovery of a more satisfactory therapy.

Download Full-text

Prostaglandin E2-binding sites and cAMP production in porcine fundic mucosa

AJP Gastrointestinal and Liver Physiology ◽

10.1152/ajpgi.1981.241.4.g313 ◽

1981 ◽

Vol 241 (4) ◽

pp. G313-G320

Author(s):

B. L. Tepperman ◽

B. D. Soper

Keyword(s):

Adenylate Cyclase ◽

Prostaglandin E2 ◽

Binding Site ◽

Binding Sites ◽

Biologically Active ◽

Cyclase Activity ◽

Adenylate Cyclase Activity ◽

Scatchard Analysis ◽

Fundic Mucosa ◽

Stimulation Of

Biologically active [3H]prostaglandin E2 (PGE2) bound rapidly and specifically to membrane fractions from hog fundic mucosa. Optimal binding occurred in the 30,000-g membrane preparation at 37 degrees C (pH 5.0). Scatchard analysis of specific PgE2 binding revealed the presence of a heterogeneous population of binding sites with Kd values and binding site concentrations of approximately 1 X 10(-9) M and 1 fmol/mg prot and 2 X 10(-8) M and 20 fmol/mg prot, respectively. Specific binding was inhibited by the following agents in descending order of potency: PGE1, PGA2, PGD2, 6-keto-PGF1 alpha, and thromboxane B2. Trypsin treatment or boiling reduced or abolished specific PGE2 binding. PGE2 stimulated cAMP formation in the 2,500-g fraction, with an approximate Km of 1 X 10(-6) M, but stimulation of adenylate cyclase activity by PG was not evident in the 16,000-g or 30,000-g tissue preparations. These results suggest that a specific PGE2-binding site exists in the 16,000-g and 30,000-g fractions of porcine fundic mucosa, although an increase in cAMP-forming capacity could not b of 1 X 10(-6) M, but stimulation of adenylate cyclase activity by PG was not evident in the 16,000-g or 30,000-g tissue preparations. These results suggest that a specific PGE2-binding site exists in the 16,000-g and 30,000-g fractions of porcine fundic mucosa, although an increase in cAMP-forming capacity could not b of 1 X 10(-6) M, but stimulation of adenylate cyclase activity by PG was not evident in the 16,000-g or 30,000-g tissue preparations. These results suggest that a specific PGE2-binding site exists in the 16,000-g and 30,000-g fractions of porcine fundic mucosa, although an increase in cAMP-forming capacity could not be localized in these fractions in vitro.

Download Full-text