Endocrinology, Vol 131, 1777-1781, Copyright © 1992 by Endocrine Society

ARTICLES

The presence of glandular kallikrein in rabbit fetal placental conditioned medium [published erratum appears in Endocrinology 1992 Dec;131(6):3026]

KM Weerasinghe and JE Gadsby
Department of Anatomy, Physiological Sciences, and Radiology, North Carolina State University College of Veterinary Medicine, Raleigh 27606.

Glandular (tissue) kallikreins are known to be involved in the posttranslational modification of protein hormones and growth factors in addition to their classical role as the bradykinin-releasing enzyme in tissues. They have been shown to be present in many tissues, such as the pancreas, salivary glands, pituitary, and testes. The objective of this study was to investigate the presence of kallikrein in the rabbit placenta. Day 21 pregnant rabbit fetal placentae were teased apart in medium 199, washed thoroughly, and incubated in fresh medium for 6 h at 37 C. The resulting placental conditioned medium (FPI) was found to have 31.35 +/- 4.3 U glandular kallikrein-like amidolytic activity/mg protein toward the chromogenic peptide substrate S-2266 (1 U is defined as the amount of p-nitroaniline liberated by 10 ng rat urinary kallikrein). Using an enzyme-linked immunosorbent assay with sheep serum raised against rat urinary kallikrein, the glandular kallikrein concentration of FPI was estimated to be 4.56 +/- 0.857 micrograms/mg protein. Upon Western blot analysis, FPI gave a positive band of 45,000 in the presence of beta-mercaptoethanol. In the absence of beta- mercaptoethanol, a band of 138,000 was observed, indicating that in FPI, kallikrein is present bound to a high mol wt binding protein. These results strongly indicate the presence of glandular kallikrein in rabbit fetal placentae.