From Big Medical Encyclopedia


chorion cover, afterbirth; lat. lac, lactis milk - f-Greek soma, soma-tos a body - f-tropos the direction; hormone[s] \HLSG; synonym: placental lactogen, chorionic somatomammotrophin, chorial-matomammotropny about hormone, somatomammotrophin, a horiomammotro-pin) — the proteinaceous hormone of a placenta having lactogenic, luteotropic and some somatotroppnpo-dobny activity.

The first reported about existence in a placenta of prolaktinpodobny proteins of Y. Ito and Higasi (To. Hi-gashi) in 1961. Working along with them, Yosimovich (J. Century of Josimo-vicli) and J. A. Maclaren in 1962 published data that blood serum of pregnant women contains substance, immunological and chemically similar to pituitary Somatotropinum (see. Somatotropic hormone), a cut cosecretes a placenta. Is later HLSG called originally placental lactogen, was it is allocated from a placenta of the person in pure form, and in 1971 its chemical structure was established.

Molecule HLSG represents the unary polypeptide chain consisting of 191 akhminokis-lotny rests with two intramolecular disulfide bridges. Pier. weight (weight) 21 000 — 23 000. The rupture of one disulfide bridge by recovery and alkylation does not influence or poorly influences on biol. activity of HLSG, but a rupture of two bonds leads to its inactivation. Apprx. 50% peptide appreciate HLSG has conformation of o '-spirals. On chemical structure of HLSG it is very similar to pituitary Somatotropinum. From 191 amino-acid rests in these two hormones completely match 163 that makes apprx. 86% of their peptide chain. Spatial structure of HLSG less rigid, than at Somatotropinum of the person and easily is exposed to irreversible changes at various physical. - chemical and chemical influences with partial or total loss biol. activities of hormone. The nucleotide sequence of a gene of HLSG defining its biosynthesis is established.

HLSG is one of the intensively synthesizablest proteins of a placenta. It is synthesized in a reinforced zone of a syntrophoblast (see the Placenta). On Chard's hypothesis (T. Chard, 1976), the level of hormone is in direct dependence on the mass of a trophoblast, concentration of protein in intervillous spaces, edges, in turn, is defined by the speed of a blood-groove. The regulating impact on synthesis of HLSG is exerted also by other factors (the hyperglycemia and vnutriamnioti-chesky administration of prostaglandins reduce the content of hormone, the considerable hypoglycemia raises it). According to a number of researchers, these changes can be non-constant and poorly expressed in comparison with similar reactions of Somatotropinum. In a placenta two types of HLSG depot, one of are revealed to-rykh it is released immediately after stimulation.

Synthesis and secretion of HLSG begin with the 6th week of pregnancy and gradually increase to 35th not de - put. Concentration of HLSG at pregnancy fluctuates from 1 mkg/ml in the first trimester to 8 — 12 mkg / ml-v the third trimester (at considerable individual fluctuations). Within the last 3 — 4 weeks of pregnancy constancy of concentration HLSG and a nek-swarm its decrease by the time of childbirth is observed. In several hours after the delivery the maintenance of HLSG in blood of mother falls to very low values. The maintenance of HLSG increases by 2 — 3 times at two-fetal and strongly increases (by 5 — 10 times) at five-fetal pregnancy. Practically all HLSG cosecretes in blood of mother as its content in blood of a fruit by 100 — 1000 times, and in an amniotic fluid is 10 times less. Secretion of HLSG a placenta has no circadian rhythms, characteristic of other hormones. Speed of exchange of HLSG in an organism considerably surpasses exchange of other proteinaceous hormones, and time of his semi-life in circulation makes from 10 — 20 to 20 — 30 min.

The mechanism of action of HLSG neiz-1 vesten since it unlike other hormones at interaction with receptors does not cause increase in tsAMF. Biol. effect of hormone is diverse. In various experiments on animal HLSG finds the weak somatotropic activity equal to 0,1 — 1% of activity of Somatotropinum of the person. Causes noticeable anabolic effect and a delay of HLSG nitrogen only at long introduction in high doses. At introduction in a daily dose of 400 mg within 12 months-.' HLSG stimulates growth of patients with a cerebral and pituitary nanism in the same degree, as by 200 times a smaller dose of Somatotropinum of the person.

HLSG is growth hormone of pregnancy that indirectly под^ tverzhdatsya by decrease at pregnancy of secretion of Somatotropinum even at the stimulation (a hypoglycemia, administration of arginine, etc.) increasing in usual conditions the content of hormone in blood. Possessing kontrinsu-lyarny and lipotropic action, HLSG increases the content of glucose, fat to - t and ketone bodies in blood of mother and thus promotes the best supply of a fruit with energy. The changes of a metabolism caused by HLSG are aimed at providing normal growth and fetation and supply with its nutrients even in conditions when the organism of mother lacks them. E.g., at the starvation increasing secretion of XJICF a placenta, hormone causes increase in blood of mother of the low-molecular nutrients capable to get through a placental barrier and to be used in energy balance of a fruit.

Aktogenny activity of HLSG makes JI, according to various researchers, from 20 to 75 — 100% of activity of prolactin (see the II ro-lactine). It consists in stimulation of growth and development of mammary glands, and then and in induction of a lactation (see JI an aktation).

HLSG also plays a part in immunol. compatibility of mother and fruit.

Exact quantitative definition of HLSG is possible only in specialized laboratories. Thanks to high concentration of HLSG in blood of pregnant women for its definition sometimes use not really sensitive methods based on suppression of passive hemagglutination, fixation of the complement and radial immunodiffusion. However broader use was found various radioimmunol. methods of definition of HLSG (see. Radio immunological method). The usual antiserum on HLSG finds cross-reaction with somatotropic hormone therefore standard radioimmunol. methods define both hormones together. Are developed radioimmunol. methods of separate definition of two hormones.

Definition of HLSG in blood is important predictive criterion. Decrease in concentration of HLSG is noted in group of women with high perinatal mortality of a fruit, at a perenashivaniye of pregnancy, threat of an abortion and the adverse course of pregnancy, and also at alimentary proteinaceous insufficiency. Reduction of maintenance of HLSG in blood serum of mother indicates lower than 4 mkg/ml at simultaneous low concentration of estrogen in 95% of cases a pre-natal growth inhibition of a fruit. Nek-roye decrease in concentration of HLSG in blood is revealed at the smoking women. Strengthening of HLSG is noted at pregnant women with a diabetes mellitus against the background of increase in the sizes of a placenta. Cases of ectopic secretion of HLSG are described by tumors of various localization.

Resolved for a wedge, uses of drug of hormone in a crust, time is not present.

Bibliography: Biochemistry of hormones and hormonal regulation, under the editorship of N. A. Yudaye-va, page 44, M., 1976; Endocrinology of pregnancy, ed. by F. Fuchs a. A. Klopper,

Phi ladelphia, 1983; Hormonal proteins and peptides, ed. by of Page H. Li, v. 4, p. 61, N. Y. a. o., 1977. Yu. A. Pankov.