Breast Cancer Research and Treatment

, Volume 4, Issue 2, pp 129–136 | Cite as

Prolactin levels and molecular heterogeneity in rat strains with high and low incidence of DMBA-induced mammary tumors

  • D. M. Lawson
  • N. Sensui
  • D. H. Haisenleder
  • P. N. Kaufman
  • R. R. Gala
Report

Summary

We compared the following parameters in Long-Evans (LE) and Sprague-Dawley (SD) female rats: 1) mammary tumor incidence after DMBA, 2) plasma prolactin (PRL) during the estrous cycle before and after DMBA, 3) plasma PRL in immature females from 0900 hr on day 29 to 0900 hr on day 30, 4) plasma PRL from 1200 to 1700 hr and before and 10 min after i.p. TRH administration in ovariectomized (OVX) rats treated with 200 µg polyestradiol phosphate (PEP), 5) anterior pituitary (AP) PRL concentration in OVX rats treated with 200µg PEP, and 6) levels and Sephadex G-100 gel filtration patterns of plasma PRL 10 min after i.p. TRH administration in OVX rats treated with 200µg PEP. We observed marked mammary tumor incidence in SD rats from one supplier (S-SD, Spartan) (96%) compared to SD from another supplier (CRSD, Charles River) (40%) or LE rats (10%). Plasma PRL was significantly decreased on metestrus-diestrus and increased on proestrus-estrus in SD (both suppliers) but not in LE rats 90 days after DMBA compared to rats not given DMBA and sacrificed at same stages of the estrous cycle on day 55 of age. Immature LE and SD-CR females exhibited significant late afternoon and early morning prolactin surges on days 29–30 whereas SD-H rats had either no surges or poorly synchronized surges at the same times. Ovariectomized mature females of the tumor-resistant strains had significantly more AP PRL than the tumor-sensitive strain when given PEP, however there were no differences between the strains in estrogen-induced afternoon PRL surges or in TRH-induced PRL release in the mature OVX, PEP-treated rats. On the other hand, Sephadex G-100 gel filtration patterns of plasma PRL in OVX LE and the tumor-resistant SD group treated with PEP and sacrificed 10 min after TRH administration were markedly different when compared with tumorsensitive SD rats. These studies indicate that there are differences in PRL secretion between strains of rats with high and low mammary tumor incidence but not all of these differences are directly related to the variation in tumorigenesis. The most promising parameters appear to be PRL secretion in immature rats and molecular heterogeneity of plasma PRL. These factors are currently under further investigation.

Keywords

DMBA genetic strains mammary tumors molecular heterogeneity prolactin rats 

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Copyright information

© Martinus Nijhoff Publishers 1984

Authors and Affiliations

  • D. M. Lawson
    • 1
  • N. Sensui
    • 1
  • D. H. Haisenleder
    • 1
  • P. N. Kaufman
    • 1
  • R. R. Gala
    • 1
  1. 1.Department of PhysiologyWayne State University School of MedicineDetroitUSA

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