M. Seppälä

Leteinizing hormone-releasing factor (LRF)-like immunoreactivity in rat pancreatic islet cells

Abstract Luteinizing hormone-releasing factor (LRF)-like immunoreactive material was demonstrated by the three-layer immunoperoxidase method in formalin-fixed tissue sections of the rat pancreas. Anti-LRF antiserum was prepared in rabbits by immunizing with synthetic LRF coupled to bovine serum albumin (BSA). The immunoreactive site of LRF reacting with antiserum resided between residues Tyr 5 and Gly 10 -NH 2 . A positive staining reaction was observed in the islet cells with the use of anti-LRF antiserum after solid phase immunoadsorption with BSA, whereas no staining was observed when adjacent control sections were prepared with anti-LRF antiserum after immunoadsorption with an LRF-BSA conjugate, or with rabbit anti-oxytocin antiserum. LRF-like immunoreactive material was isolated from the rat pancreata by methanol extraction. This material coeluted with synthetic and hypothalamic LRF in cation exchange chromatography on carboxymethyl cellulose, and dilutions of it gave an inhibition curve parallel to that of synthetic LRF in radioimmunoassay. The concentration of LRF-like material in the rat pancreas is 1.1 pg/mg wet weight. These results suggest that LRF or a closely LRF-related peptide is shared by the central nervous system and the gastrointestinal tract.

MEASUREMENT OF PLACENTAL PROTEIN 5, PLACENTAL LACTOGEN AND PREGNANCY-SPECIFIC β1 GLYCOPROTEIN IN MID-TRIMESTER AS A PREDICTOR OF OUTCOME OF PREGNANCY

The circulating levels of placental protein 5 (PP5), placental lactogen (hPL) and pregnancy‐specific β1‐glycoprotein (SP1 were measured in 254 women at the 16th week of pregnancy and the levels were correlated to fetal outcome in late pregnancy. A significant association was shown between high PP5 levels and premature delivery, and low SP1 levels and intrauterine growth retardation. Measurement of placental proteins in the first half of pregnancy may be a valuable clinical index of fetal outcome in late pregnancy.

Placental protein 5 is related to blood coagulation and fibrinolytic systems

Previous studies have shown that placental protein 5 (PP5) forms complexes with heparin. In order to further elucidate the biological role of PP5 we studied the effect of plasmin and thrombin on the immunoreactivity of PP5, and the possible functional antiplasmin and antithrombin effects of purified PP5. Varying concentrations of plasmin and thrombin were added to pregnancy plasma, and the PP5 levels, measured by radioimmunoassay, were found to be elevated by 558% (plasmin and 48-87% (thrombin). Incubation of radiolabeled PP5 with plasmin resulted in the formation of radioactive fragments with smaller molecular weights. Functional studies using a chromogenic substrate confirmed that purified PP5 has an antiplasmin activity. An average increase of 15% was observed in the antiplasmin activity when 200 ng purified PP5 was added to 150 microliters of pregnancy serum. Thus, there are certain similarities between PP5 and antihrombin III. Both form complexes with heparin and have antiplasmin properties, and both were found to be heat labile. But, functional studies utilizing a chromogenic substrate failed to demonstrate any antithrombin III-like activity in the purified PP5 preparation that had antiplasmin activity. Our results show that the function of PP5 is related to the blood coagulation and fibrinolytic systems, at least through its inhibitory action on plasmin.

Immunohistochemical demonstration of placental protein 5 (PP5) -like material in the seminal vesicle and the ampullar part of vas deferens

Abstract Placental protein 5 (PP5), originally isolated from normal placenta (1), has recently been identified in the seminal plasma (2). We undertook a series of immunohistochemical experiments in order to find out the source of the seminal plasma PP5-immunoreactive material. Immunoperoxidase staining for PP5 was positive in the ampullar part of vas deferens and the seminal vesicle, while testis, epididymis, vas deferens, seminal vesicle, prostate and urethra were negative.

Identification of luteinizing hormone-releasing factor and alpha-subunit of glycoprotein hormones in human pancreatic islets

Abstract Using an immunoperoxidase technique, staining of human pancreatic islets was observed with antisera to luteinizing hormone-releasing factor (LRF) and to the glycoprotein hormones hCG, LH and the alpha-subunit. Treatment of fixed tissue sections with protease inhibitors or heat did not affect the staining indicating that the positive results were not a non-specific effect of protease activity in vitro. No staining was observed in the islets with antisera against the beta-subunit of LH, FSH or hCG suggesting that the material which stained was free alpha-subunit rather than native hormone. The association of LRF and alpha-subunit in human pancreatic islets raises the possibility of a functional relationship between the two in this site.

THE EFFECTS OF PROTAMINE ON SERUM LEVELS OF PLACENTAL PROTEIN 5 (PP5) IN NORMAL AND ABNORMAL PREGNANCY: A POSSIBLE RELATION TO COAGULATION ABNORMALITIES

The levels of placental protein 5 (PP5) in pregnancy serum show an apparent increase after the addition of protamine sulphate. The difference of the apparent concentrations of serum PP5 in the presence and absence of protamine (ΔPP5) was determined in 345 normal and abnormal pregnancies. A positive ΔPP5 was less frequent in diabetic pregnancy (45 per cent) and pre‐eclampsia (57 per cent) than in normal pregnancy (80 per cent). These findings provide further evidence that PP5 may be involved in the coagulation system, and in particular may relate to abnormal coagulation processes at the placental site.

Elevated prolactin levels in oral contraceptive pill-related hypertension.

Twenty women whose blood pressure became elevated during oral contraceptive treatment had higher serum prolactin levels (31 +/- 5.3 microgram/liter) than did 20 normotensive pill takers (16.1 +/- 1.8 microgram/liter) and 20 women who were not taking the pill (14 +/- 1.1 microgram/liter), and the higher level was maintained (30 +/- 3.5 microgram/liter) after the pill was discontinued and blood pressure had become normal. This increase in prolactin levels was not related to differences in age or mode of treatment, and it is thought to reflect an alteration in dopaminergic transmission in patients with pill-related hypertension.

The Lancet: PREGNANCY-SPECIFIC β-GLYCOPROTEIN IN COMPLICATIONS OF EARLY PREGNANCY

Abstract Maternal concentrations of pregnancy-specific β 1 -glycoprotein (SP 1 ) were measured in 145 patients with vaginal bleeding in the first trimester of pregnancy. The levels of SP 1 were substantially reduced in cases in which the outcome was unsatisfactory. The sensitivity of the test was 65%, the predictive value 96%, and the specificity 98%; these results are at least as good as those of other biochemical tests of this type. It is concluded that measurement of SP 1 is useful in diagnosis, even when ultrasound findings are also available. However, in a small group of subjects both ultrasound and biochemical findings were normal, despite an unfavourable outcome, and it seems likely that such cases are beyond the reach of any present diagnostic measure.