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Reprod. Nutr. Dev.
Volume 41, Number 6, November-December 2001
Page(s) 505 - 511
DOI: 10.1051/rnd:2001105

Reprod. Nutr. Dev. 41 (2001) 505-511

Heterogeneity of circulating prolactin in the bitch

Cristina Gobelloa, b, Miriam Colombanic, Hugo Scagliac, Rodolfo L. De La Sotaa and Rodolfo G. Goyab

a  Institute of Theriogenology, Faculty of Veterinary Sciences, National University of La Plata, 60th and 118th Streets, CC 296, La Plata 1900, Argentina
b  INIBIOLP-Histology B, Faculty of Medicine, National University of La Plata, 60th & 118th Streets, La Plata 1900, Argentina
c  IABE, La Plata, 1900, Argentina

(Received 30 July 2001; accepted 12 November 2001)

Different molecular forms of circulating prolactin (PRL) are known to occur in several species. As no such information was available in dogs, we assessed the molecular profile of circulating PRL in bitches. Pooled sera from covertly (CTRL) and overtly pseudopregnant (PSPT) diestrous bitches with high or low ( > 10 or < 10 ng $\cdot$mL -1, respectively) serum PRL (measured by ELISA) were analyzed by Sephadex G-100 and Concanavalin A-Sepharose column chromatography. Four serum PRL fractions were identified and termed big-big, big ( > 67 kDa), native (23 kDa) and fragmented ( < 20 kDa) PRL. The percentages of these fractions were roughly similar in CTRL and PSPT animals, irrespective of their serum PRL levels (higher in PSPT than in CTRL bitches). A large proportion of glycosylated PRL (between 69 and 100%) was also detected in these sera. We conclude that in dogs, circulating PRL occurs in multiple molecular forms, whose relative abundance is comparable in covertly and overtly pseudopregnant bitches.

Hétérogénéité de la prolactine circulante chez la chienne. La prolactine (PRL) circulante se trouve, dans différentes espèces, sous plusieurs formes moléculaires. Compte tenu du fait qu'il n'existe pas d'information disponible chez le chien, nous avons décidé d'étudier le profil moléculaire de la PRL circulante chez cet animal. Nous avons utilisé des pools de sérums provenant de chiennes normales en diestrus (CTRL) ou pseudogestantes (PSPT), ayant des taux élevés ou bas de PRL ( > 10 ou < 10 ng $\cdot$mL -1 respectivement; dosages effectués par Elisa). Les sérums ont été analysés sur colonne de Séphadex G-100 et par chromatographie d'affinité, sur colonne de Sépharose couplée à de la Concanavaline A. La chromatographie sur G-100 a identifié quatre fractions de PRL, qui ont été appelées big-big, big (PM < 67 kDa), native (23 kDa) et fragmentée ( < 20 kDa). Les pourcentages relatifs de ces fractions sont identiques chez les CTRL et les PSPT, quel que soit le taux, élevé ou bas, de PRL sérique (plus haut chez les animaux CTRL). De plus, une proportion importante de PRL sérique (69 à 100 %) est sous forme glycosylée. En conclusion, la PRL sérique se trouve, chez le chien, sous des formes moléculaires multiples, dont l'abondance relative est comparable chez la chienne normale et pseudogestante.

Key words: prolactin / molecular variants / bitch / diestrus / pseudopregnancy

Mots clés : prolactine / variant moléculaire / chienne / diestrus / pseudogestation

Correspondence and reprints: Cristina Gobello

© INRA, EDP Sciences 2001

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