Calcitonin-like immunoreactivity and calcitonin gene expression in the placenta and in the mammary gland of the rat.
Recently, the presence of monomeric CT in plasma and milk was reported by others in a lactating woman surgically thyroidectomized. Similarly, the placenta was thought to be a possible source of CT. Since such findings were based exclusively on immunological arguments, we have investigated the CT gene expression in these rat tissues. CT mRNAs were detected by dot-blot hybridization of total RNAs extracted from rat tissues with a 32P-labelled human CT cDNA probe. Subcellular fractions of each tissue were screened for CT-like immunoreactivity using two different antibodies. With one antibody, extracts of the mammary gland and placenta both produced full displacement of labelled human CT from the antiserum and serial dilutions of the extracts gave displacement curves parallel to that of synthetic human CT, which suggests immunological similarity. However, dilution curves were not parallel for the second antibody, and for both antisera, CT-like immunoreactivity was found in all subsellular fractions from nuclei to cytosols. Immunoprecipitation of translation products from poly (A)+RNAs of placenta showed two major bands around 30 kD. Under stringent conditions, the weak hybridization of placental RNAs seen by dot-blot under less stringent conditions disappeared. Northern analyses of total RNAs from the placenta failed to detect mRNA of 1 k base size like in thyroid glands, but hybridization under weak stringent conditions occurred with larger mRNAs (around 4.4 and 2.4 k bases). Immunoprecipitation of translation products from mRNAs of rat mammary glands showed three major bands around 46, 30 and 20 kD. Dot-blot hybridization of total RNAs extracted from mammary glands was also negative.(ABSTRACT TRUNCATED AT 250 WORDS)
Jousset
V
V
Endocrinologie Moléculaire et Métabolique, UA CNRS 1123, Université Pierre et Marie Curie, Paris, France.
Legendre
B
B
Besnard
P
P
Segond
N
N
Jullienne
A
A
Garel
J M
JM
D000818:Animals; D001345:Autoradiography; D002116:Calcitonin / Q000235:genetics / Q000276:immunology / Q000378:metabolism*; D004247:DNA / Q000032:analysis; D005260:Female; D008321:Mammary Glands, Animal / Q000378:metabolism*; D009693:Nucleic Acid Hybridization; D010920:Placenta / Q000378:metabolism*; D012313:RNA / Q000032:analysis; D012333:RNA, Messenger / Q000032:analysis; D051381:Rats; D011919:Rats, Inbred Strains; D013347:Subcellular Fractions / Q000378:metabolism
D012333:RNA, Messenger; D012313:RNA; D002116:Calcitonin; D004247:DNA