Differential effects of subcutaneous estrogen and progesterone on low-density lipoprotein size and susceptibility to oxidation in postmenopausal rhesus monkeys.
OBJECTIVE
To study the differential effects of subcutaneous E2 alone or in combination with P on the susceptibility of low-density lipoprotein (LDL) cholesterol to oxidation in naturally postmenopausal diet-controlled rhesus monkeys.


METHODS
Prospective, longitudinal controlled study.


METHODS
Oregon Health Sciences University, Portland, Oregon, and Oregon Regional Primate Research Center, Beaverton, Oregon.


METHODS
Five naturally postmenopausal rhesus monkeys.


METHODS
Estradiol was administered subcutaneously for the first 4 weeks, followed by E2 plus P for 4 weeks, followed by a third 4-week washout period.


METHODS
Changes in plasma lipoprotein levels and oxidation of LDL and serum concentrations of E2 and P.


RESULTS
Levels of LDL cholesterol fell after 4 weeks of treatment with E2, compared with baseline. The lag time to half maximal light absorbancy after 4 weeks of E2 treatment was significantly increased compared with baseline. The maximal absorbance values and the slope of the propagation phase after 4 weeks of treatment with E2 were decreased compared with baseline. After 4 weeks of combined E2 and P treatment, all values were comparable to baseline.


CONCLUSIONS
These results suggest that subcutaneous E2 therapy appears to enhance LDL resistance to oxidation and that this effect is attenuated by the addition of the P.
McKinney
K A
KA
Department of Obstetrics and Gynecology, Oregon Health Sciences University, Portland, USA.
Duell
P B
PB
Wheaton
D L
DL
Hess
D L
DL
Patton
P E
PE
Spies
H G
HG
Burry
K A
KA
D000818:Animals; D004958:Estradiol / Q000008:administration & dosage / Q000494:pharmacology*; D005260:Female; D008077:Lipoproteins, LDL / Q000378:metabolism*; D008137:Longitudinal Studies; D008253:Macaca mulatta; D017698:Postmenopause / Q000378:metabolism*; D011374:Progesterone / Q000008:administration & dosage / Q000494:pharmacology*; D011446:Prospective Studies
D008077:Lipoproteins, LDL; C099252:oxidized low density lipoprotein; D011374:Progesterone; D004958:Estradiol