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. 2001 Mar;119(2):54-8.
doi: 10.1590/s1516-31802001000200003.

Effects of hypertension on maternal adaptations to pregnancy: experimental study on spontaneously hypertensive rats

J C Peraçoli  1 , M V Rudge, M S Sartori, R J da Silva Franco
Affiliations

Effects of hypertension on maternal adaptations to pregnancy: experimental study on spontaneously hypertensive rats

J C Peraçoli et al. Sao Paulo Med J. 2001 Mar.

Abstract
in English, Portuguese

Context: Animal models for essential hypertension have been used for understanding the human pathological conditions observed in pregnant hypertensive women.

Objective: To study the possible effects of pregnancy on hypertension and of hypertension on pregnancy in spontaneously hypertensive rats (SHR), and in their normotensive Wistar-Kyoto (WKY) counterparts.

Type of study: Comparative study using laboratory animals.

Setting: Animal Research Laboratory of Clinical Medicine at the Medical School of Botucatu, São Paulo State University, Brazil.

Sample: Ten to twelve-week-old virgin female normotensive Wistar-Kyoto (WKY) rats and spontaneously hypertensive rats (SHR). The animals were separated into four groups: 15 pregnant spontaneously hypertensive rats (SHR-P), 10 non-pregnant spontaneously hypertensive rats (SHR-NP), 15 pregnant normotensive rats (WKY-P), and 10 non-pregnant normotensive rats (WKY-NP).

Main measurements: The blood pressure was evaluated by the tail cuff method, in rats either with or without prior training for the handling necessary for tail cuff measurements. The maternal volume expansion was indirectly evaluated by weight gain, and by systemic parameters as hematocrit, hemoglobin, total protein, albumin and sodium retention. The perinatal outcome of pregnancy was evaluated by analysis of resorptions, litter size, rate of low weight and number of stillbirths.

Results: The late fall in blood pressure in the pregnant SHR strain and in the normotensive WKY strain can only be detected in rats previously trained to accept the handling necessary for the tail cuff measurement. During pregnancy the body weight gain was significantly higher in WKY than in SHR rats. Systemic parameters were significantly lower in pregnant WKY rats than in non-pregnant WKY rats, while no differences were observed between pregnant and non-pregnant SHR groups. In pregnant WKY rats the sodium retention was higher from the 13th day onwards, while in SHR rats this occurred only on the 21st day. The characteristics of reproductive function such as number and weight of fetus, perinatal mortality and the resorption rate were significantly affected in the SHR strain.

Conclusion: The SHR strain may be considered as a model for chronic hypovolemic maternal hypertension, with the fetal growth retardation being determined by this hypovolemic state.

CONTEXTO:: Os modelos animais de hipertensão arterial têm sido usados para a compreensão das condições patológicas humanas encontradas nas mulheres grávidas hipertensas.

OBJETIVO:: Estudar os possíveis efeitos da prenhez sobre a hipertensão arterial, e desta sobre a prenhez, em ratas espontaneamente hipertensas (SHR) e seu controle normotenso Wistar-Kyoto (WKY)

TIPO DE ESTUDO:: Estudo comparativo com animais de laboratório.

LOCAL:: Laboratório de pesquisa experimental da Faculdade de Medicina de Botucatu, Universidade Estadual de São Paulo, Brasil.

AMOSTRA:: Foram utilizadas ratas virgens, das linhagens WKY e SHR, com idade entre 10 e 12 semanas. Os animais foram divididos em quatro grupos: 15 SHR-prenhe (SHR- P), 10 SHR não-prenhe (SHR-NP), 15 WKY prenhe (WKY-P) e 10 WKY não-prenhe (WKY-NP).

VARIÁVEIS ESTUDADAS:: A pressão arterial foi avaliada pelo método do esfigmomanômetro de cauda em ratas adaptadas ou não previamente ao aquecimento necessário para a medida da pressão arterial da cauda. A expansão da volemia foi avaliada indiretamente pelo ganho de peso e por parâmetros sistêmicos como hematócrito, hemoglobina, proteínas totais, albumina e balanço de sódio. O resultado perinatal foi avaliado pelo número de nódulos de reabsorção, tamanho da ninhada, taxa de fetos com baixo peso e número de natimortos.

RESULTADOS:: A queda da pressão arterial no final da prenhez, das ratas SHR e WKY, ocorreu somente nas ratas adaptadas ao aquecimento para a medida da pressão arterial na cauda. Durante a prenhez o ganho de peso materno foi significativamente maior nas ratas WKY. Os parâmetros sistêmicos foram significativamente menores nas ratas WKY prenhez em relação ao seu controle não-prenhe, não sendo observada diferença significativa entre as ratas SRH prenhes e não-prenhes. Nas ratas WKY prenhez a retenção de sódio foi maior desde o décimo terceiro dia de prenhez, e nas ratas SHR apenas a partir do décimo nono dia. Os aspectos reprodutivos como número e peso dos fetos, mortalidade fetal e número de nódulos de reabsorção foram significativamente afetados na linhagem SHR.

CONCLUSÃO:: A linhagem SHR pode ser considerada como modelo de hipertensão arterial crônica hipovolêmico, sendo a restrição do crescimento fetal observada, conseqüente a esse estado de hipovolemia materna.

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Conflict of interest statement

Conflict of interest: Not declared

Figures

Figure 1
Figure 1. Blood pressure levels of SHR and WKY rats measured every second day of the experiment from day 7 up to day 21. The results are expressed as the mean of 12 animals evaluated per period. * P < 0.05 in relation to WKY strain; # P < 0.05 in relation to SHR-P, WKY-NP and WKY-P and @ P < 0.05 in relation to WKY-NP (ANOVA).
Figure 2
Figure 2. Blood pressure levels of SHR and WKY rats measured on days 0,7,14 and 21 of the experiment. The results are expressed as the mean of 10-15 animals evaluated per period. * P < 0.05 in relation to WKY strain (ANOVA)
Figure 3
Figure 3. Body weight of the SHR and WKY rats evaluated on days 0, 7, 14 and 21 days of the experiment. The results are expressed as the mean of 12 animals evaluated per period. * P < 0.05 in relation to WKY-NP; # P < 0.05 in relation to SHR-NP and @ P < 0.05 in relation to SHR-P (ANOVA).
Figure 4
Figure 4. Weight gain of WKY and SHR rats measured on day 21 of the experiment. The results are expressed as mean of 10-15 animals. * P < 0.05 in relation to WKY-NP, SHR-NP and SHR-P, and # P < 0.05 in relation to SHR-NP and WKY-NP (ANOVA).
Figure 5
Figure 5. Sodium balance of the SHR and WKY rats measured in different periods of the experiment. The results are expressed as mean of 10-15 animals evaluated per period. * P<0.05 in relation to SHR-P; @ P<0.05 in relation to WKY-NP; # P<0.05 in relation to SHR-NP (ANOVA)
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