The effects of progesterone on intermediary carbohydrate metabolism in the rabbit

by Chen, Mee-jin

The effects of a single dose of progesterone wi thin the pbysiologioa.l range (2.5 mgfkg and 5 mg/kg) on intermediary metabolism was studied. For this purpose, the blood gluoose, plasma non-esterified fatty acids (BrA) aJ3d plasma alpha amino acid nitrogen oonoentr&t ions were measured in unan&esthetized fast ing normal and adrenaleD1iomized virgin rabbits, with blood samples oolleoted from the ear before the injection of progesterone and at intervals of half, one, two, three and. five hours afterwards. In addition, the gluoose uptake by isolated diaphragm am. the gluoose output by isolated liver from progesterone-treated rabbits were determined, and the insulin sensitivity test in rabbits given progesterone was also performed.

During an experimental period of 5 hours a single intra,muscular injeotion of 2.5 mgjkg of progesterone caused in normal rabbits a signifioant increase in the blood gluoose level a.t one

and five hours, while a dose of 5 mgfkg of progesterone oaused a pronounoed rise of the blood glucose level which persisted throughout the five-hour period. Pretreatment with an adrenergio antagonist, dih3dro ergotamine methanesulf'onate (DHE) partially diminished the ~ergl;roaemio response of the normal rabbits to a dose of 5 mgfkg

of progesterone. In adrenalectomized rabbits a dose of 5 mgfkg of progesterone bloaked the b3Perglyca.emio effect produoed in normal rabbits. These findings show that h3'Perglyoaemio response of progesterone mea- be mediated thrOU8h the action of adrenaline. When

the diaphragm and the liver were removed one hour a.:rter an intrarmuscular injection of 5 mg/kg of progesterone to normal rabbits, the gluoose uptake by the isolated d.i~hra.gm muscle was diminished

.

but the gluoose output of the liver was unaltered. Thus, the hyperglyoa.emio effect of progesterone ma;r be attribu.ted to a depression of gluoose uptake by peripheral tissue bu.t not to hepatio glyoogenolytio ao1Iion. 1Ihen a dose of 5 mg/kg of progesterone was given 3 hours betore the injeotion ot exogenous insulin, the fall

of the blood gluoose level was greater than that without pre-

treatment with progesterone, showing that progesterone potentiated

the action of insulin, probably by an inarease of the tissue

sensitivity to insulin.

A dose of 2.5 mgfkg of progesterone oaused in normal rabbits a signifioant tall of the plasma NIllB'A level at one hour after injection, while a larger dose ot 5 mgjkg of progesterone induoed a signifioant depression of the plasma NEFA oonoentration, at half, two and five hours respectively atter injeotion. Also, a rebound of plasma NEFA to above zero (fasting) ~a.:1se-line value was observed after the administration of 5 mgfkg of progesterone. }lo

Significant oorrelation was observed between the rise of the blood.

gluoose level and the fall of the plasma. NEFA level. In normal

rabbits, DHE pretreatment oompletely blooked the deorease in the plasma. ND'A level normally produoed. by 5 mgfkg of progesterone.

In normal rabbits a single injection of 2.5 mgfkg of

progesterone oaused a signifioant dearease in the plasma. alpha. amino

acid nitrogen level at ~. hours, while?a dose of 5 mg/kg of progesterone oaused a more pronounoed deorease in the plasma amino acid nitrogen level at two, three and five hours respectively. DB pretreatment 18 d to a part ial blockade of the decrease in the plasma amino acid nitrogen level induoed by injection of 5 mg/kg of progesterone. The mechanisms of the decrease in the plasma Nllli'A level and the amino acid nitrogen level in progesterone-induoed hTPergly'oaemi9o are not olear without further studJ'.