Secretagogue-dependent and -independent transport of zinc hydration forms in rat parietal cells

Abstract

Prolonged exposure to gastric acid is a leading cause of gastroesophageal reflux disease (GERD) and esophagitis. With the ever increasing number of patients showing insensitivity to proton-pump-inhibitor (PPI) therapy with recurrence of symptoms over time, alternative treatment options remain an important issue. Previous studies from our laboratory have shown that a zinc sulfate salt can inhibit HCl generation at the cellular level of the parietal cell. In this paper, we examine the difference between two hydration forms of ZnSO (monohydrate HO and heptahydrate 7HO) in their entry characteristics into the parietal cell under several physiological conditions associated with acid secretion. Using the Zn sensitive fluorochrome Newport Green, we examined the rate of Zn entry in Δfluorescent units/second (ΔFU/second), at two different concentrations for both hydration states on both fasted and non-fasted animals. In a separate series of studies, we examined the effects of secretagogues on the entry rates and transport mechanisms. Exposure of the secretagogue carbachol transformed the resting parietal cell to an activated state and represents a stimulated condition through the neuronal pathway. The hormonal activation of the parietal cell was achieved by using histamine. Non-fasted conditions were considered to be a state between hormonal and neuronal activation. To demonstrate that ZnSO enters the parietal cell through the NKCC1 co-transporter, the inhibitor bumetanide was applied during secretagogue-stimulated acid secretion. Both salts, monohydrate and heptahydrate ZnSO, show a concentration-dependent cell entry under all conditions studied. During stimulated acid secretion, induced through either the neuronal or the hormonal pathway, heptahydrate ZnSO enters the parietal cell significantly faster than monohydrate ZnSO, whereas monohydrate ZnSO exhibits faster entry during resting conditions in fasted animals. At 30 μM following stimulation with histamine, heptahydrate ZnSO enters the cell faster than monohydrate ZnSO (ΔFU/second 30 μM = 1.782, ΔFU/second 30 μM = 1.038, respectively). Three hundred micromolar, heptahydrate ZnSO shows a faster entry into the cells (ΔFU/second = 4.02407) compared to monohydrate ZnSO (ΔFU/second = 3.225) following exposure to carbachol. The mechanism of entry of both salts was found to be predominantly via the basolateral NKCC1 transporter with the rate of zinc entry decreasing to minimal values (ΔFU/second = 0.275) after application of bumetanide during stimulated conditions.

Induction of Secretagogue Independent Gastric Acid Secretion via a Novel Aspirin-Activated Pathway

“…To investigate the direct cellular effect of aspirin on parietal cell acid secretion, we undertook studies using fasted rats with ad lib access to fluids (Ferstl et al, 2016). To assay acid secretion, we used the pH-sensitive dye BCECF to give semi-real time measurements of proton extrusion in glands exposed to aspirin.…”

“…During the experimental cycle, the fluorescent signal was monitored at 530 ± 10 nm every 10 s with the help of an intensified charge-coupled device camera. Individual images and intensity values were recorded along with the emission data showing the 440/490 ratio for real-time intensity measurements (Kopic et al, 2012; Ferstl et al, 2016). At the end of the cycle, cells were calibrated with the High K + /Nigericin calibration technique to calculate the pH from the emission data as described in previous studies (Boron et al, 1994).…”

Activation of Secretagogue Independent Gastric Acid Secretion via Endothelial Nitric Oxide Synthase Stimulation in Rats

“…Thus, L-arginine can be considered as a potential causative agent for these gastrointestinal diseases and excessive L-arginine intake can lead to severe disadvantages for the stomach. Other, well-known causes are non-steroidal anti-inflammatory drugs (NSAIDs), nicotine, alcohol, caffeine, stress and infections [33-36]. Since the prevalence of gastroesophageal ailments is continuously increasing in the United States [37], new findings about causative agents are of highly interest.…”

Zinc Deficiency and Therapeutic Value of Zinc Supplementation in Pediatric Gastrointestinal Diseases

“…Zinc sulfate [116,119,123] Human/animal 1. A 5-day pre-treatment with zinc sulfate (50 or 150 mg/kg/day) reduced the rate, number, and area of cystamine-induced duodenal lesions (rats) [116].…”