OBJECTIVETo investigate the effect of low-frequency ultrasound in promoting milk secretion in rats during lactation.

METHODSTwenty-four lactating SD rats feeding 10 suckling rats each were randomly allocated into 3 groups, namely the control group (with sham irradiation), 5 min group (with ultrasonic irradiation of the breast for 5 min daily), and 10 min group (irradiation for 10 min daily). The mammary glands of the rats were consistently irradiated by low-frequency ultrasound (40 kHz, 0.26 W/cm(2)) for 7 days since the 2nd day after delivery. The milk yield, average body weight gain of the offspring, mammary gland index, serum prolactin (PRL) and breast histology were examined.

RESULTSThe milk yield, body weight gain of offspring, mammary gland index and serum PRL concentration in 10 min group were significantly greater than those in the control group and 5 min group (P<0.05). Compared with the other two groups, the 10 min group showed significantly increased acinar gland expansion and acinar number.

CONCLUSIONLow-frequency ultrasound can promote milk secretion in lactating rats, suggesting its potential as a new approach of physical therapy for promoting milk secretion.