| Breast milk is the best natural food for offspring, sufficient qualifiedbreast milk is the guarantee for infant’s survival and health. Breastfeeding isof great significance for the health both of mother and child. Recently, theincidence of postpartum hypogalactia tends to rise because of some factors.General clinical treatment for postpartum hypogalactia includesgalactagogue, acupuncture＆massage, and the physical methods throughmodern medical instruments. For being free from side or toxic effectaroused by drugs, the physical methods is worthy of promotion. Theultrasonic physiotherapy, as a mature physical way, has been applied topromoting for wound healed, soft tissue repaired, skin aging refreshed andthe fracture healed. Yet neither domestic nor international relevant literatureabout its application to the treatment of postpartum hypogalactia has beenfound. The overloaded lactation model in rats were used in this study forinvestigating the galactagogue effect of low frequency ultrasound on ratsduring lactation and discussing primary mechanism of galactagogue effectaroused by low-frequency ultrasound, thus it would be providing sometheoretical and experimental basis for treatment of postpartum hypogalactia by low-frequency ultrasound.Objectives1. To establish the model of overloaded lactation in rats for providing aefficient, reliable method used in the assessment of promoting milksecretion function in this research.2. To study the effect of low frequencyultrasound on the lactating production of lactation rats in order to investigateits feasibility of application using in treatment of postpartum hypogalactia.3.To discuss primary mechanism of galactagogue effect with low-frequencyultrasound.Methods1.The Sprague Dawley(SD) lactating rats and their pups were used.①Selecting the intervals for each breast feeding:38rats with each10pups fedat a litter were randomly divided into3groups according to differentlactation intervals of4h,5h and6h. The daily milk yield calculated by thelitter weight difference before and after breast-feeding, and the mortalityof offspring were determined consistently for10days.②Selecting pupsnumber of each litter:42rats were randomly divided into4groups, whichdifferently fed6,8,10,12pups for each female rat. The daily milk yield wasconsistently observed for10days. The average body weight gain andmortality of offspring were calculated.2.24SD lactating rats which fed10pups at a litter were randomlydivided into3groups (n=8):control group (sham irradiation),5min group (ultrasonic irradiation for5minutes/breast· d) and10min group(ultrasonic irradiation10minutes/breast·d). Mammary gland of rats wereconsistently irradiated by low frequency ultrasound (40kHz,0.26w/cm2)from the2nd day after delivery for7days. The milk yield, average bodyweight gain of offspring, mammary gland index, serum prolactin (PRL)and breast histology were investigated. Semi-quantitative image analysiswas applied to investigate the expression level of PRLR.3. The serum and mammary glands of female rats in step2werecollected. The concentration of serum prolactin was detected byenzyme-linked immunosorbent assay(ELISA). The immunohistochemistry(IHC) were taken to detect the expressions of PRLR in female rats’mammary tissue. Semi-quantitative image analysis was applied toinvestigate the expression level of PRLR.Results1.①Offspring mortality: The mortalities in groups of6h and5h(separation) interval were26.3%and15.8%, higher than those of4h groupwith3%. Milk yield: That in6h group was30.93g, significantly greater thanthe28.8g and27.62g respectively from those of4h and5h group (P <0.01);There was no significant difference between those of4h and5h groups(P>0.05).②Offspring mortality: Those in both6/litter,8/litter groups were0%, those in10/litter group and12/litter group were3%and25%. Milkyield: The milk yield respectively was20.1g,25.42g,27.63g of6,8,10/litter groups. The differences among the3groups were significant (P <0.01).That in the12/litter group was28.22g, significantly higher than those ofgroups of6/litter and8/litter (P <0.01), and there was no significantdifference when compared with10/litter group (P>0.05). Offspring bodyweight gain: which in6/litter group and8/litter group respectively was6.55g and6.14g and showed no significant difference betweenthem(P>0.05). Those in10/litter group and12/litter group respectively was4.54g and3.58g, showed significant difference(P <0.01) between eachother and significantly lower than those of6/litter and8/litter groups(P<0.01).2. The milk yield, body weight gain of offspring, mammary glandindex and concentration of PRL in serum of10min group weresignificantly greater than those in control group and5min group(P<0.05);Compared with those in the other two groups, the acinar glands expandedand the acinar number increased in10min group under the lightmicroscope.3. The concentration of PRL in serum in10min group wassignificantly higher than those in control group （P<0.01） and5mingroup(P<0.05). The Immunohistochemical staining andimmunofluorescence showed that the expressions of the PRLR in rats’mammary glands of ultrasonic irradiation groups were stronger than those incontrol group. The Semi-quantitative image analysis showed that the expressions in10min group were significantly greater than those in controlgroup and5min group（P<0.01).Conclusions10pups of each litter,4hours of separation intervals can truly reflectthe milk yield, which were appropriate for the overloaded lactation in ratsfor lactagogue function evaluating.A certain dose of low frequency ultrasonic irradiation can effectivelypromote milk secretion of overloaded lactation in rats. The potentialmechanisms are as follows: The low-frequency ultrasound can stimulatethe PRL secretion and increase the expressions of PRLR, promotemammary epithelial cell proliferation and breast development, thus toincrease the milk production. Therefore, the low frequency ultrasound isexpected to become a new optional secure physical therapy for promotingmilk secretion. |
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