Two distinct placental lactogen-like substances in serum during mid-pregnancy in the rat.
Two forms of placental lactogen (PL), designated PL-I and PL-II, have been reported in the serum of pregnant rats; PL-I was secreted during mid-pregnancy and PL-II was secreted near term. In the present study, we found that two distinct forms with PL-like activity were secreted into the blood during mid-pregnancy. Serum from day-12 pregnant rats was subjected to high-performance liquid chromatography (HPLC) gel-filtration (TSK-G3000SswXL column), and PL activity was assayed by radioreceptor assay using 125I-labeled rat PRL and hepatocyte plasma membrane from pregnant rats. HPLC-gel filtration separated the PL activity into two peaks with mol wt of 55-60 K and 45-50 K, as estimated by reference to the elution volume of standard proteins. We tentatively designated these peaks PL-alpha and PL-beta, respectively. Considering these mol wt, PL-beta seemed to be identical to PL-I. mRNA was extracted from samples of placenta obtained each day from day 8 to day 12 of pregnancy and analyzed by means of a translation system involving micro-injection into Xenopus oocytes. The time of appearance of the mRNAs corresponding to PL-alpha and PL-beta did not correspond and differed according to the day of pregnancy, suggesting that there are individual mRNAs for each PL in rat placenta. Treatment of PL-alpha and PL-beta with peptide: N-glycosidase F completely abolished the binding activity to their receptors. Also since they were sensitive to glycosidases such as endoglycosidase H, endoglycosidase F and neuraminidase, these PLs were considered to possess N-linked glycoresidue(s) and to be sialylated.(ABSTRACT TRUNCATED AT 250 WORDS)
Furuyama
N
N
Laboratory of Veterinary Physiology, University of Tokyo, Japan.
Shiota
K
K
Takahashi
M
M
D000704:Analysis of Variance; D000818:Animals; D002851:Chromatography, High Pressure Liquid; D002852:Chromatography, Ion Exchange; D005260:Female; D008970:Molecular Weight; D010920:Placenta / Q000378:metabolism; D010928:Placental Lactogen / Q000032:analysis / Q000097:blood* / Q000302:isolation & purification; D011247:Pregnancy; D011270:Pregnancy, Animal / Q000097:blood*; D014176:Protein Biosynthesis; D012333:RNA, Messenger / Q000096:biosynthesis / Q000302:isolation & purification; D011869:Radioligand Assay; D051381:Rats; D017208:Rats, Wistar
D012333:RNA, Messenger; D010928:Placental Lactogen