title: Cyclic AMP-dependent protein kinase in rat mammary tissue: expression of catalytic and regulatory subunits throughout pregnancy and lactation.
abstract: 'Expressed' and 'total' activities of cyclic AMP-dependent protein kinase (PK-A) were measured in extracts of rat mammary tissue sampled throughout pregnancy and lactation. Expression of the genes encoding the catalytic subunit (C-subunit) isoforms C alpha and C beta was examined by Northern blotting, as a function of mammary development, to determine relative levels of their respective mRNAs. The content of C-subunit protein (all isoforms) was estimated immunochemically and related to levels of C-subunit catalytic activity and of mRNAs. It was found that C-subunit isoform mRNAs are expressed co-ordinately during mammary development and that a marked decline in expression, per cell, at around parturition is paralleled by a fall in 'total' PK-A activity. The 'expressed' activity of PK-A activity underwent characteristic changes throughout pregnancy and lactation, reaching a peak late in pregnancy. The PK-A activity ratio reached a peak in early lactation. C-subunit protein mass closely parallel 'total' PK-A activity throughout pregnancy and lactation, thereby demonstrating the constancy of C-subunit specific catalytic activity during these developmental events. Regulatory subunits (R-subunits) were probed with the photoaffinity label 8-azido-[32P]cAMP. The abundance of R-II as a proportion of total R-subunit increased throughout pregnancy and lactation, and quantitative analysis of the photoaffinity labelling suggested inconstancy in the ratio of R:C subunits, with highest values occurring in late pregnancy/early lactation.
authors.affiliation: Hannah Research Institute, Scotland, U.K.
authors.forename: R A
authors.initials: RA
authors.lastname: Gardner
authors.forename: M T
authors.initials: MT
authors.lastname: Travers
authors.forename: M C
authors.initials: MC
authors.lastname: Barber
authors.forename: W R
authors.initials: WR
authors.lastname: Miller
authors.forename: R A
authors.initials: RA
authors.lastname: Clegg
mesh_terms: D000345:Affinity Labels; D000818:Animals; D001386:Azides / Q000378:metabolism; D015152:Blotting, Northern; D002384:Catalysis; D000242:Cyclic AMP / Q000031:analogs & derivatives / Q000378:metabolism; D017868:Cyclic AMP-Dependent Protein Kinases / Q000235:genetics / Q000378:metabolism*; D005260:Female; D015870:Gene Expression; D007774:Lactation / Q000502:physiology*; D046911:Macromolecular Substances; D008321:Mammary Glands, Animal / Q000201:enzymology*; D011247:Pregnancy; D011270:Pregnancy, Animal / Q000378:metabolism*; D012333:RNA, Messenger / Q000032:analysis / Q000378:metabolism; D051381:Rats; D017208:Rats, Wistar; D012045:Regulatory Sequences, Nucleic Acid
chemical_list: D000345:Affinity Labels; D001386:Azides; D046911:Macromolecular Substances; D012333:RNA, Messenger; C017042:8-azidoadenosine-3',5'-monophosphate; D000242:Cyclic AMP; D017868:Cyclic AMP-Dependent Protein Kinases