CHOOSING AMONG DIFFERENT TECHNICAL VARIATIONS OF PERCOLL CENTRIFUGATION FOR SPERM SELECTION

We compared the efficiency of different methodological variations of t he centrifugation through discontinuous Percoll gradients (PC) to impr ove semen samples in the laboratory. Five different combinations of th e number, volume and density of PC layers were assayed in 14 semen sam ples presenting various qualities. Each specimen was divided into five aliquots and processed simultaneously. The percentage of spermatozoa showing optimal movement (VAP > 30 mu m s(-1) and STR > 80% ) after PC selection when the number of gradients was reduced to three or two (P C-3: 43.3%, PC-2: 41.3%) and when the volume of layers was diminished to 0.5 ml (mPC-3: 44.2%, and mPC-2: 48.1%), was higher than in classic al columns with four gradients of 1 ml (PC-4: 26.3%). The absolute rec overy of optimal sperm was better with PC-2, mPC-2 and mPC-3. In sampl es showing low concentration or motility of spermatozoa, mPC-2 was the most effective technique. PC-2 and mPC-2 showed a tendency to elimina te more red blood cells contaminating the samples. Straight line veloc ity and straightness were similarly improved by all the methods. We co nclude that the technique of PC centrifugation with only two gradients is simpler and more effective for sperm selection and in cases of poo r samples can be used with low-volume layers.