Swimming Exercise Protocol and Care Methods for Pregnant Rats

Published: April 05, 2024

doi:

Ziqi Ni*¹, Jiaqi Cao*¹, Meiling Shan, Yanyan Zhang^2,3, Lijun Shi^2,3

¹Department of Exercise Physiology,Beijing Sport University, ²Laboratory of Sports Stress and Adaptation of General Administration of Sport,Beijing Sport University, ³Key Laboratory of Physical Fitness and Exercise, Ministry of Education,Beijing Sport University

Summary

Here, we present a protocol to delineate rat breeding methods, swimming training procedures, and post-breeding nursing protocols for pregnant rats after training. This protocol provides an animal model for studying the effects of maternal exercise during pregnancy on offspring and its underlying mechanisms.

Abstract

The developmental origins of health and disease concept highlights the impact of early environments on chronic non-communicable diseases like diabetes, cardiovascular disease, and cancer. Studies using animal models have investigated how maternal factors such as undernutrition, overnutrition, obesity, and exposure to chemicals or hypoxia affect fetal development and offspring health, leading to issues like low birth weight, high blood pressure, dyslipidemia, and insulin resistance. Given the increasing prevalence of overweight and obesity among reproductive-age women, effective interventions are critical. Maternal exercise during pregnancy has emerged as a key intervention, benefiting both mother and offspring and reducing the risk of disease. This study compares the differences of three exercise models on pregnant rats: voluntary wheel running, motorized treadmills, and swimming. Swimming is the most beneficial option due to its safe and controlled intensity levels. This protocol details the rat breeding methods, swimming training during pregnancy, and post-breeding nursing protocols. This model, suitable for various rat and mouse species, is useful for studying the benefits of maternal exercise on offspring health and intergenerational wellness.

Introduction

The Developmental Origins of Health and Disease (DOHaD) concept emerged over the last two decades, which has shown that environmental influences during early development affect the risk of later pathophysiological processes associated with chronic non-communicable disease (NCD), especially diabetes, cardiovascular disease, and some types of cancer¹. During the most plastic phase of fetal development, where offspring are exposed to the intrauterine environment, the gene and environment interaction and uteroplacental perfusion are crucial factors of fetal reprogramming². Previous studies have predominantly utilized animal models to investigate the detrimental effects, such as maternal undernutrition, overnutrition, or obesity during pregnancy, and prenatal exposure to chemicals or hypoxia, on fetal development and long-term phenotypic effects in the offspring³. This produced low birth weight and later growth and produced adverse effects on offspring, including elevated blood pressure, dyslipidemia, and insulin resistance⁴. Since the rate of overweight and obesity is rapidly increasing among women of reproductive age, establishing effective interventions to prevent the intergenerational transmission of these deleterious maternal disorders is urgently needed, which has an important impact on population health⁵^,⁶.

Exercise has long been recognized as an important preventive therapeutic for type 2 diabetes, hypertension, and several other diseases⁷. Exercise during pregnancy has beneficial effects for the mother and confers beneficial effects on offspring, thus reducing the maternal transmission of disease to offspring⁸. Several years of research have demonstrated exercise's safety and profound benefits, including substantial reductions in common pregnancy conditions such as gestational diabetes mellitus⁹^,¹⁰. Regarding maternal and fetal safety, conducting exercise training and post-nursing protocols is challenging.

David¹¹ et al. described animal exercise models applicable to cardiovascular health research. The three commonly used exercise models, voluntary wheel running, motorized treadmills, and swimming, have advantages and disadvantages. The voluntary wheel running closely mimics the locomotor behavior of rats, enabling them to move according to their circadian rhythm. However, this sort of exercise needs more precise regulation of intensity and duration. The motorized treadmill can control exercise intensity, volume, and duration, but sometimes it needs electric stimulation, which may trigger physical and psychological stress in the animals. Swimming is widely used in rodent studies due to the inherent swimming ability of rats, which can also avoid electric stimulation or mechanical damage to their feet and tails¹². In studies on prenatal exercise models¹³^,¹⁴, swimming is a commonly used exercise modality. As pregnancy progresses and the abdomen of the rat swells, treadmill and wheel running exercises may cause repeated contact of the abdomen with hard surfaces. In contrast, the water environment in swimming provides buoyancy, reducing the risk of exercise-related injuries for pregnant animals.

This protocol presents the rat breeding methods, how to perform the swimming training during pregnancy, and the post-breeding nursing protocols for pregnant rats after training. This pregnant swimming training model can be applied to a wide range of rat and mouse species, which may thus provide a useful rodent model for future investigation using animal-based models to study the mechanisms regulating the beneficial effects of maternal exercise on offspring health and the benefits of exercise across generations.

Protocol

All methods described here have been approved by the animal ethical committee at Beijing Sport University and carried out in compliance with the National Institutes of Health (NIH) guidelines and the Chinese animal protection laws and institutional guidelines. 1. Mating and feeding rats Purchase specific pathogen-free (SPF) rated 10-week-old Wistar female rats and 11-week-old Wistar male rats. Implement adaptive feeding: Feed the Wistar rats ad libitu…

Representative Results

In the rat breeding methods section (Figure 1), we determine the estrous cycle of female rats by making vaginal secretion slides to increase the success rate of breeding. The rats' estrous cycle lasts 4-5 days, including proestrus, estrus, metestrus, and diestrus. Female rats in metestrus or diestrus exhibit behaviors such as distancing themselves from males. At the same time, those in estrus are willing to mate, and ovulation in female rats mostly occurs at the end of estrus. During pro…

Discussion

This study aims to establish a feasible exercise program for pregnant rats, including detailed rat mating methods, swimming training protocols, and research methods to evaluate physiological indicators in fetuses. We have developed a prenatal swimming exercise training model through practice, with corresponding solutions to potential issues that may arise in the protocol (Table 1). This protocol will make it more practical and assist researchers in establishing prenatal exercise models.

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Disclosures

The authors have nothing to disclose.

Acknowledgements

This work was supported by the National Natural Science Foundation of China (32071174, 32200941, 32371183, and 31771312).

Materials

Caliper	Mitutoyo Measuring Instruments (Shanghai) Co., Ltd	530-101 N15	Fetus dissect
Circular water bucket	Naliya	N/A	Rat swimming
Experimental Surgical Instrument	Shenzhen RWD Life Technology Co., LTD	SP0001-G	Fetus dissect
Glass Microscope Slides	Jiangsu Shitai experimental equipment Co., LTD	80312-3161	Vaginal smear
Glass petri dish	Merck Life Technologies	BR455751-10EA	Offspring rearing
Hairdryer	Panasonic	EH-WNE5H	Post-swimming care
Information Card	Zhongke Life Science	SS3	Rat mating
Isoflurane	Shenzhen RWD Life Technology Co., LTD	R510-22-10	Fetus dissect
Light microscope	Olympus	IX71-F22PH	Vaginal smear
Mating cage	Zhongke Life Science	SS3	Rat mating
Medical Absorbent Cotton	Hongxiang Sanitary Materials Co., LTD	N/A	The pregnant rats are anticipating giving birth
Rodent Anesthesia Machine, Gas Anesthesia	Shenzhen RWD Life Technology Co., LTD	R500IE	Fetus dissect
Rodent breeding feed	Beijing Huafukang Biotechnology Co., LTD	1032	Pregnant rat feeding
Rodent maintenance feed	Beijing Huafukang Biotechnology Co., LTD	1022	Offspring rearing
Rodent sunflower seeds	Jolly	JP241	Nutritional supplement
Soundproof cotton	Kufu Medical Instrument	N/A	The pregnant rats are anticipating giving birth
Sterile Cotton Swab (2 mm diameter)	Kufu Medical Instrument	N/A	Vaginal smear
Sterile gauze	Kufu Medical Instrument	N/A	Fetus dissect
Stroke-physiological Saline Solution (0.9% NaCl)	Shandong Hualu Pharmaceutical Co., LTD	N/A	Vaginal smear
Thermometer	Beekman organism	N/A	The monitoring of rat swimming
Towels	Grace	N/A	Post-swimming care
Transparent plastic container	Naliya	N/A	Swimming adaptive training
Ultraviolet light	Merck Life Technologies	Z169633-1EA	Post-swimming care
Water heater	Haier	EC6001-Q6S	Rat swimming
Weight Scale	Electronlc Acale	JM.A10001	Body weight measurement
Wistar Rats	Vital river Laboratory Animal Technology Co., LTD	N/A	Experiment

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