Synthesis and Secretion of A-Type Natriuretic Peptide in the Auricular Cardiocytes during Pregnancy and Lactation in Mouse.

Abstract

. A-type (atrial) natriuretic peptide (ANP) levels in the auricular cardiocytes and plasma were examined by immunohistochemistry, electron microscopy, and radioimmunoassay in pregnant and lactating mice. Additionally, the cardiocyte ANP mRNA expression was measured by the polymerase chain reaction method. ANP-immunoreactivity (IR) and the number of ANP-granules in the cardiocytes on the 18th day of gestation were greater than those in virgin controls, but the plasma ANP concentration decreased on the 18th day of gestation. On the day of delivery, ANP-IR and the number of ANP-granules in the cardiocytes were decreased compared to those during the pregnancy and to those in virgin controls, and then began to increase continually until the 15th day of lactation. Plasma ANP concentration after delivery was significantly higher than that during pregnancy, and than that in virgin controls, and continued to increase until the 15th day of lactation. Cardiocyte ANP mRNA expression was highest on the day of delivery compared to that in all the other times. In conclusion, these results suggested that the circulating systems of ANP during pregnancy and lactation were regulated differentially. nonpregnant, nonlactating controls. Moreover, we have examined the ANP mRNA levels in atrial cardiocytes to determine any change in the synthesis system of ANP during these periods. MATERIALS AND METHODS Animals:The heart and blood were obtained from 10 pregnant mice of the ICR strain (Jcl: ICR, CLEA Japan, Inc., Osaka, Japan) in each group on the 10th and 18th day of gestation, and from 10 lactating mice (same strain) in each group on the day of delivery, and on the 5th, 15th and 21st day after delivery. The day of insemination was defined as 0-day of gestation, and the day of delivery was regarded as 0-day of lactating. Normal vergin mice were used as control. All animals were kept in automatically controlled rooms (temperature: 24 ± 1°C; humidity: 55 ± 5%; automatic lighting: 6:00 a.m. to 8:00 p.m.) and fed with a pellet diet CE-2 (CLEA Japan, Inc., Osaka, Japan) and water ad libitum. These animals were sacrificed under sodium pentobarbital anesthesia (50 mg/kg, i. p.) and their hearts and blood were removed. All experiments were undertaken in accordance with Guide for Animal Experimentation, Kurume University.Immunohistochemistry: The left auricular tissue blocks were fixed in Zamboni's solution for 24 hr at 4°C. After washing with 0.15 M phosphate-buffered saline (PBS) at pH 7.3, they were dehydrated, embedded in paraffin and sectioned at 5 µm. Prior to immunohistochemical staining, the deparaffinized sections were incubated in absolute A-type (atrial) natriuretic peptide (ANP) is a circulating hormone with a wide range of biological effects, including natriuresis, diuresis and vasodilation, and it may play an important role in the regulation of blood pressure and body fluid homeostasis [5,12,29]. This peptide hormone is mainly produced and stored within secretory granules in the atrial cardiocytes [5,11,[21][22][23]. Dist...

Effectiveness of Angiotensin-Converting Enzyme Inhibitor or Angiotensin II Receptor Blocker on Atrial Natriuretic Peptide

“…For ANP and GAPDH standards, we used a cDNA dilution series synthesized with RNA extracts from the atrial tissue of untreated rats. 6 For ANP-cDNA and GAPDH-cDNA, 10 L of DNA solution was added to 25 L of reaction mixture (Taq Man universal PCR Mastermix, Applied Biosystems, Roche, USA), containing 13.5 L of DDW, 0.5 L of each primer, 0.5 L of TaqMan probe. The thermal cycler conditions were as follows: 50°C for 2 min, 95°C for 10 min, 45 cycles of 95°C for 15 s, and 50°C for 1 min for both ANP and GAPDH.…”