The growth hormone/prolactin gene family in ruminant placentae

Abstract

Ruminant placentae produce at least two distinct subclasses of the growth hormone/prolactin gene family, the placental lactogens and prolactin-related proteins. Placental lactogens have been purified from cattle, goat and sheep placentae, and the amino acid sequences of bovine and ovine placental lactogen are known. Bovine and ovine placental lactogens are structurally more similar to prolactin than they are to growth hormone. In addition, six unique mRNAs have been described in cattle that encode prolactin-related proteins that are structurally distinct from ruminant placental lactogens. All characterized ruminant placental lactogens and prolactin-related proteins are products of chorionic binucleate cells, but specific biological functions of these placental hormones have not been elucidated. Ovine placental lactogen may modify maternal and fetal intermediary metabolism to provide energy substrates to the fetus. Bovine placental lactogen has been implicated as a luteotropic agent, and is also capable of stimulating mammogenesis and lactogenesis. No ruminant placental lactogen receptor has been structurally characterized, although they are presumed to be similar to either the growth hormone or prolactin receptor. Available technologies will allow many of the questions regarding the regulation, mechanism of action and function of these placental hormones to be addressed.

Nutrient restriction during late gestation reduces milk yield and mammary blood flow in lactating primiparous beef females

“…Gestational mammary development and lactational mammary function are both under strict endocrine regulation by reproductive and metabolic hormones ( Svennersten-Sjaunja and Olsson, 2005 ), which can be influenced by nutrition. The bovine placenta synthesizes large quantities of hormones such as estrone, progesterone, and placental lactogen ( Anthony et al, 1995 ; Schuler et al, 2008 ). In an induced lactation model in dairy heifers, recombinant placental lactogen stimulated mammary growth and differentiation ( Byatt et al, 1994 ) and increased milk production ( Byatt et al, 1997 ).…”

Expressão das conexinas 32 e 43 em células trofoblásticas da placenta bovina em cultura celular

“…Assim, as células trinucleadas e as da placa sincicial são polarizadas para depositar os grânulos próximos à circulação materna. Estes grânulos têm hormônios como lactogênio placentário (DUELLO et al, 1986;BECKERS, 1987;ANTHONY et al, 1995). No útero bovino, os locais do lactogênio placentário são específicos do epitélio glandular endometrial que expressa receptores de prolactina (STEWART et al, 2000;NOEL et al, 2003).…”

“…Isso implica que o lactogênio placentário pode ter um papel importante na estimulação da morfogênese endometrial da glândula e função diferenciada durante a prenhez nos ruminantes, e isso pode facilitar o crescimento e desenvolvimento fetal. Acredita-se que além do lactogênio placentário, as células binucleadas possam produzir outros hormônios como prolactina relacionada à proteína-1 (ZIELER et al, 1990;KESSLER et al, 1991;ANTHONY et al, 1995), glicoproteinas associadas à gestação (ZOLI et al, 1991;ZOLI et al, 1992;GREEN et al, 2000), estradiol (MATAMOROS et al, 1994) e progesterona (REIMS et al, 1985;WANGO et al, 1991 (GROSS et al, 1983;NICHOLSON et al, 1997;BUULTJENS et al, 1988;GOODENOGH et al, 1996). Estudos mais recentes, com purificação das áreas de junções comunicantes e avaliação de DNA, identificaram mais de 18 membros dessa família, bem como a distribuição destes em células e tecidos específicos (SHIBATA et al, 2001).…”