LH pattern in ovariectomised rats after continuous blood withdrawal: effects of different substitutions.

Plasma concentrations of LH and of sodium, potassium, total protein and haemoglobin were measured in ovariectomised rats during continuous blood withdrawal up to 180 min; 0.45 ml blood samples were taken every 10 min, the total volume of blood removed not exceeding 9 ml. Four groups of animals were studied: group A received no substitution (controls), group B was substituted with 0.9% NaCl-solution, group C with 3.5% polypeptide solution (Haemaccel), and group D with a suspension of washed erythrocytes from the blood removed. During blood withdrawal, the mean values of LH concentrations as well as the amplitudes of the rhythmic LH pulses remained constant in all the animals. However, the rate of pulses was reduced in the control animals and in the group receiving 0.9% NaCl-solution during the period between 90 and 180 min; in contrast no change was observed in the groups C and D during the whole period. The results presented here show that the characteristic LH pattern in ovariectomised rats is not affected by volume depletion, provided the blood is replaced by a solution containing either a polypeptide or a suspension of washed erythrocytes.